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	$240.52	5.449%	$253.6259	$253.63	$253.65	$253.60
Purchase #2	$82.63	9.450%	$90.4385	$90.44	$90.45	$90.40
Purchase #3	$152.82	6.244%	$162.3621	$162.36	$162.35	$162.40
Purchase #4	$121.51	11.464%	$135.4399	$135.44	$135.45	$135.40
Purchase #5	$120.73	11.748%	$134.9134	$134.91	$134.90	$134.90
Purchase #6	$72.27	13.715%	$82.1818	$82.18	$82.20	$82.20
Purchase #7	$98.87	5.718%	$104.5234	$104.52	$104.50	$104.50
7 purchase totals =	$889.35		$963.4850	$963.48	$963.50	$963.40