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	$189.40	5.154%	$199.1617	$199.16	$199.15	$199.20
Purchase #2	$239.35	10.121%	$263.5746	$263.57	$263.55	$263.60
Purchase #3	$61.97	5.869%	$65.607	$65.61	$65.60	$65.60
Purchase #4	$57.76	11.802%	$64.5768	$64.58	$64.60	$64.60
Purchase #5	$95.83	6.141%	$101.7149	$101.71	$101.70	$101.70
Purchase #6	$118.70	5.152%	$124.8154	$124.82	$124.80	$124.80
Purchase #7	$64.79	9.809%	$71.1453	$71.15	$71.15	$71.10
7 purchase totals =	$827.80		$890.5957	$890.60	$890.55	$890.60