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	$81.53	11.535%	$90.9345	$90.93	$90.95	$90.90
Purchase #2	$194.47	6.593%	$207.2914	$207.29	$207.30	$207.30
Purchase #3	$127.91	12.389%	$143.7568	$143.76	$143.75	$143.80
Purchase #4	$122.66	9.154%	$133.8883	$133.89	$133.90	$133.90
Purchase #5	$159.64	12.692%	$179.9015	$179.90	$179.90	$179.90
Purchase #6	$191.36	6.554%	$203.9017	$203.90	$203.90	$203.90
Purchase #7	$127.85	11.232%	$142.2101	$142.21	$142.20	$142.20
7 purchase totals =	$1,005.42		$1,101.8843	$1,101.88	$1,101.90	$1,101.90