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	$90.48	8.805%	$98.4468	$98.45	$98.45	$98.40
Purchase #2	$227.59	5.263%	$239.5681	$239.57	$239.55	$239.60
Purchase #3	$169.72	10.851%	$188.1363	$188.14	$188.15	$188.10
Purchase #4	$194.58	7.226%	$208.6404	$208.64	$208.65	$208.60
Purchase #5	$153.72	3.254%	$158.722	$158.72	$158.70	$158.70
Purchase #6	$52.29	10.463%	$57.7611	$57.76	$57.75	$57.80
Purchase #7	$47.78	10.328%	$52.7147	$52.71	$52.70	$52.70
7 purchase totals =	$936.16		$1,003.9894	$1,003.99	$1,003.95	$1,003.90