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	$101.67	4.562%	$106.3082	$106.31	$106.30	$106.30
Purchase #2	$115.74	4.169%	$120.5652	$120.57	$120.55	$120.60
Purchase #3	$61.92	6.844%	$66.1578	$66.16	$66.15	$66.20
Purchase #4	$124.51	5.125%	$130.8911	$130.89	$130.90	$130.90
Purchase #5	$178.54	4.832%	$187.1671	$187.17	$187.15	$187.20
Purchase #6	$72.26	8.561%	$78.4462	$78.45	$78.45	$78.40
Purchase #7	$64.79	10.223%	$71.4135	$71.41	$71.40	$71.40
7 purchase totals =	$719.43		$760.9491	$760.96	$760.90	$761.00