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	$157.78	9.163%	$172.2374	$172.24	$172.25	$172.20
Purchase #2	$65.58	9.723%	$71.9563	$71.96	$71.95	$72.00
Purchase #3	$23.86	10.288%	$26.3147	$26.31	$26.30	$26.30
Purchase #4	$37.43	4.536%	$39.1278	$39.13	$39.15	$39.10
Purchase #5	$141.89	6.641%	$151.3129	$151.31	$151.30	$151.30
Purchase #6	$211.67	7.727%	$228.0257	$228.03	$228.05	$228.00
Purchase #7	$51.96	10.339%	$57.3321	$57.33	$57.35	$57.30
7 purchase totals =	$690.17		$746.3069	$746.31	$746.35	$746.20