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	$35.98	3.607%	$37.2778	$37.28	$37.30	$37.30
Purchase #2	$71.82	8.678%	$78.0525	$78.05	$78.05	$78.10
Purchase #3	$85.27	5.586%	$90.0332	$90.03	$90.05	$90.00
Purchase #4	$215.93	5.546%	$227.9055	$227.91	$227.90	$227.90
Purchase #5	$46.77	6.110%	$49.6276	$49.63	$49.65	$49.60
Purchase #6	$64.92	9.421%	$71.0361	$71.04	$71.05	$71.00
Purchase #7	$150.59	10.216%	$165.9743	$165.97	$165.95	$166.00
7 purchase totals =	$671.28		$719.9070	$719.91	$719.95	$719.90