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	$212.73	8.298%	$230.3823	$230.38	$230.40	$230.40
Purchase #2	$51.77	12.219%	$58.0958	$58.10	$58.10	$58.10
Purchase #3	$196.64	7.533%	$211.4529	$211.45	$211.45	$211.50
Purchase #4	$152.49	13.181%	$172.5897	$172.59	$172.60	$172.60
Purchase #5	$61.95	4.165%	$64.5302	$64.53	$64.55	$64.50
Purchase #6	$206.86	12.496%	$232.7092	$232.71	$232.70	$232.70
Purchase #7	$134.54	5.451%	$141.8738	$141.87	$141.85	$141.90
7 purchase totals =	$1,016.98		$1,111.6339	$1,111.63	$1,111.65	$1,111.70