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	$57.60	12.802%	$64.974	$64.97	$64.95	$65.00
Purchase #2	$126.97	13.591%	$144.2265	$144.23	$144.25	$144.20
Purchase #3	$152.70	11.402%	$170.1109	$170.11	$170.10	$170.10
Purchase #4	$231.80	7.453%	$249.0761	$249.08	$249.10	$249.10
Purchase #5	$206.28	11.550%	$230.1053	$230.11	$230.10	$230.10
Purchase #6	$77.77	11.399%	$86.635	$86.64	$86.65	$86.60
Purchase #7	$83.73	6.860%	$89.4739	$89.47	$89.45	$89.50
7 purchase totals =	$936.85		$1,034.6017	$1,034.61	$1,034.60	$1,034.60