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	$61.29	11.187%	$68.1465	$68.15	$68.15	$68.10
Purchase #2	$182.37	7.534%	$196.1098	$196.11	$196.10	$196.10
Purchase #3	$243.54	10.649%	$269.4746	$269.47	$269.45	$269.50
Purchase #4	$141.28	7.558%	$151.9579	$151.96	$151.95	$152.00
Purchase #5	$143.99	4.809%	$150.9145	$150.91	$150.90	$150.90
Purchase #6	$153.94	4.640%	$161.0828	$161.08	$161.10	$161.10
Purchase #7	$71.42	6.839%	$76.3044	$76.30	$76.30	$76.30
7 purchase totals =	$997.83		$1,073.9905	$1,073.98	$1,073.95	$1,074.00