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	$127.96	4.401%	$133.5915	$133.59	$133.60	$133.60
Purchase #2	$222.89	5.537%	$235.2314	$235.23	$235.25	$235.20
Purchase #3	$57.69	11.153%	$64.1242	$64.12	$64.10	$64.10
Purchase #4	$21.63	5.849%	$22.8951	$22.90	$22.90	$22.90
Purchase #5	$188.65	10.524%	$208.5035	$208.50	$208.50	$208.50
Purchase #6	$240.93	12.199%	$270.3211	$270.32	$270.30	$270.30
Purchase #7	$150.82	9.720%	$165.4797	$165.48	$165.50	$165.50
7 purchase totals =	$1,010.57		$1,100.1465	$1,100.14	$1,100.15	$1,100.10