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	$221.51	5.435%	$233.5491	$233.55	$233.55	$233.50
Purchase #2	$143.70	4.611%	$150.326	$150.33	$150.35	$150.30
Purchase #3	$161.79	10.812%	$179.2827	$179.28	$179.30	$179.30
Purchase #4	$143.34	3.812%	$148.8041	$148.80	$148.80	$148.80
Purchase #5	$37.34	7.809%	$40.2559	$40.26	$40.25	$40.30
Purchase #6	$41.28	11.796%	$46.1494	$46.15	$46.15	$46.10
Purchase #7	$135.71	11.666%	$151.5419	$151.54	$151.55	$151.50
7 purchase totals =	$884.67		$949.9091	$949.91	$949.95	$949.80