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	$210.68	5.553%	$222.3791	$222.38	$222.40	$222.40
Purchase #2	$121.70	5.575%	$128.4848	$128.48	$128.50	$128.50
Purchase #3	$197.47	8.822%	$214.8908	$214.89	$214.90	$214.90
Purchase #4	$172.44	9.375%	$188.6063	$188.61	$188.60	$188.60
Purchase #5	$144.43	6.409%	$153.6865	$153.69	$153.70	$153.70
Purchase #6	$22.73	11.279%	$25.2937	$25.29	$25.30	$25.30
Purchase #7	$176.49	11.361%	$196.541	$196.54	$196.55	$196.50
7 purchase totals =	$1,045.94		$1,129.8822	$1,129.88	$1,129.95	$1,129.90