Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$146.61	7.846%	$158.113	$158.11	$158.10	$158.10
Purchase #2	$158.74	6.460%	$168.9946	$168.99	$169.00	$169.00
Purchase #3	$132.91	10.854%	$147.3361	$147.34	$147.35	$147.30
Purchase #4	$119.80	9.663%	$131.3763	$131.38	$131.40	$131.40
Purchase #5	$237.67	10.709%	$263.1221	$263.12	$263.10	$263.10
Purchase #6	$136.78	11.808%	$152.931	$152.93	$152.95	$152.90
Purchase #7	$156.52	6.522%	$166.7282	$166.73	$166.75	$166.70
7 purchase totals =	$1,089.03		$1,188.6013	$1,188.60	$1,188.65	$1,188.50