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	$96.32	9.682%	$105.6457	$105.65	$105.65	$105.60
Purchase #2	$14.72	7.197%	$15.7794	$15.78	$15.80	$15.80
Purchase #3	$82.53	7.798%	$88.9657	$88.97	$88.95	$89.00
Purchase #4	$45.74	10.350%	$50.4741	$50.47	$50.45	$50.50
Purchase #5	$76.30	6.260%	$81.0764	$81.08	$81.10	$81.10
Purchase #6	$148.46	11.381%	$165.3562	$165.36	$165.35	$165.40
Purchase #7	$45.94	3.335%	$47.4721	$47.47	$47.45	$47.50
7 purchase totals =	$510.01		$554.7696	$554.78	$554.75	$554.90