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	$226.98	10.435%	$250.6654	$250.67	$250.65	$250.70
Purchase #2	$153.35	6.442%	$163.2288	$163.23	$163.25	$163.20
Purchase #3	$244.26	9.855%	$268.3318	$268.33	$268.35	$268.30
Purchase #4	$46.88	7.672%	$50.4766	$50.48	$50.50	$50.50
Purchase #5	$240.86	5.525%	$254.1675	$254.17	$254.15	$254.20
Purchase #6	$114.80	11.396%	$127.8826	$127.88	$127.90	$127.90
Purchase #7	$29.58	8.384%	$32.06	$32.06	$32.05	$32.10
7 purchase totals =	$1,056.71		$1,146.8127	$1,146.82	$1,146.85	$1,146.90