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	$81.97	13.761%	$93.2499	$93.25	$93.25	$93.20
Purchase #2	$212.45	13.862%	$241.8998	$241.90	$241.90	$241.90
Purchase #3	$42.61	13.429%	$48.3321	$48.33	$48.35	$48.30
Purchase #4	$115.40	12.849%	$130.2277	$130.23	$130.25	$130.20
Purchase #5	$124.71	12.157%	$139.871	$139.87	$139.85	$139.90
Purchase #6	$240.45	5.584%	$253.8767	$253.88	$253.90	$253.90
Purchase #7	$208.57	5.431%	$219.8974	$219.90	$219.90	$219.90
7 purchase totals =	$1,026.16		$1,127.3546	$1,127.36	$1,127.40	$1,127.30