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	$70.32	10.258%	$77.5334	$77.53	$77.55	$77.50
Purchase #2	$248.28	3.196%	$256.215	$256.22	$256.20	$256.20
Purchase #3	$118.72	9.580%	$130.0934	$130.09	$130.10	$130.10
Purchase #4	$82.52	12.792%	$93.076	$93.08	$93.10	$93.10
Purchase #5	$146.88	6.803%	$156.8722	$156.87	$156.85	$156.90
Purchase #6	$49.30	8.541%	$53.5107	$53.51	$53.50	$53.50
Purchase #7	$173.97	12.864%	$196.3495	$196.35	$196.35	$196.30
7 purchase totals =	$889.99		$963.6502	$963.65	$963.65	$963.60