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	$127.48	3.256%	$131.6307	$131.63	$131.65	$131.60
Purchase #2	$54.28	10.834%	$60.1607	$60.16	$60.15	$60.20
Purchase #3	$67.27	6.781%	$71.8316	$71.83	$71.85	$71.80
Purchase #4	$78.57	11.434%	$87.5537	$87.55	$87.55	$87.60
Purchase #5	$51.25	11.453%	$57.1197	$57.12	$57.10	$57.10
Purchase #6	$126.99	7.189%	$136.1193	$136.12	$136.10	$136.10
Purchase #7	$234.47	10.512%	$259.1175	$259.12	$259.10	$259.10
7 purchase totals =	$740.31		$803.5332	$803.53	$803.50	$803.50