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	$162.37	8.202%	$175.6876	$175.69	$175.70	$175.70
Purchase #2	$131.43	10.634%	$145.4063	$145.41	$145.40	$145.40
Purchase #3	$168.86	6.776%	$180.302	$180.30	$180.30	$180.30
Purchase #4	$126.32	13.773%	$143.7181	$143.72	$143.70	$143.70
Purchase #5	$99.93	3.240%	$103.1677	$103.17	$103.15	$103.20
Purchase #6	$196.35	12.648%	$221.1843	$221.18	$221.20	$221.20
Purchase #7	$225.94	7.501%	$242.8878	$242.89	$242.90	$242.90
7 purchase totals =	$1,111.20		$1,212.3538	$1,212.36	$1,212.35	$1,212.40