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	$20.48	11.759%	$22.8882	$22.89	$22.90	$22.90
Purchase #2	$237.83	7.674%	$256.0811	$256.08	$256.10	$256.10
Purchase #3	$145.81	5.174%	$153.3542	$153.35	$153.35	$153.40
Purchase #4	$57.59	11.507%	$64.2169	$64.22	$64.20	$64.20
Purchase #5	$190.77	10.429%	$210.6654	$210.67	$210.65	$210.70
Purchase #6	$209.90	5.354%	$221.138	$221.14	$221.15	$221.10
Purchase #7	$154.54	6.222%	$164.1555	$164.16	$164.15	$164.20
7 purchase totals =	$1,016.92		$1,092.4993	$1,092.51	$1,092.50	$1,092.60