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	$245.75	9.501%	$269.0987	$269.10	$269.10	$269.10
Purchase #2	$158.96	4.226%	$165.6776	$165.68	$165.70	$165.70
Purchase #3	$113.38	7.414%	$121.786	$121.79	$121.80	$121.80
Purchase #4	$78.41	4.800%	$82.1737	$82.17	$82.15	$82.20
Purchase #5	$79.61	6.789%	$85.0147	$85.01	$85.00	$85.00
Purchase #6	$187.28	12.629%	$210.9316	$210.93	$210.95	$210.90
Purchase #7	$112.96	9.298%	$123.463	$123.46	$123.45	$123.50
7 purchase totals =	$976.35		$1,058.1453	$1,058.14	$1,058.15	$1,058.20