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	$241.50	7.332%	$259.2068	$259.21	$259.20	$259.20
Purchase #2	$121.27	12.198%	$136.0625	$136.06	$136.05	$136.10
Purchase #3	$69.78	10.573%	$77.1578	$77.16	$77.15	$77.20
Purchase #4	$40.31	6.117%	$42.7758	$42.78	$42.80	$42.80
Purchase #5	$88.44	9.491%	$96.8338	$96.83	$96.85	$96.80
Purchase #6	$85.91	4.590%	$89.8533	$89.85	$89.85	$89.90
Purchase #7	$204.55	11.140%	$227.3369	$227.34	$227.35	$227.30
7 purchase totals =	$851.76		$929.2269	$929.23	$929.25	$929.30