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	$46.53	3.213%	$48.025	$48.03	$48.05	$48.00
Purchase #2	$165.30	12.391%	$185.7823	$185.78	$185.80	$185.80
Purchase #3	$82.72	8.673%	$89.8943	$89.89	$89.90	$89.90
Purchase #4	$234.83	10.680%	$259.9098	$259.91	$259.90	$259.90
Purchase #5	$210.37	3.645%	$218.038	$218.04	$218.05	$218.00
Purchase #6	$14.28	13.866%	$16.2601	$16.26	$16.25	$16.30
Purchase #7	$127.78	7.181%	$136.9559	$136.96	$136.95	$137.00
7 purchase totals =	$881.81		$954.8654	$954.87	$954.90	$954.90