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	$84.91	12.203%	$95.2716	$95.27	$95.25	$95.30
Purchase #2	$212.43	5.851%	$224.8593	$224.86	$224.85	$224.90
Purchase #3	$166.62	11.205%	$185.2898	$185.29	$185.30	$185.30
Purchase #4	$172.49	9.140%	$188.2556	$188.26	$188.25	$188.30
Purchase #5	$89.37	13.144%	$101.1168	$101.12	$101.10	$101.10
Purchase #6	$212.40	13.104%	$240.2329	$240.23	$240.25	$240.20
Purchase #7	$190.63	5.138%	$200.4246	$200.42	$200.40	$200.40
7 purchase totals =	$1,128.85		$1,235.4506	$1,235.45	$1,235.40	$1,235.50