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	$134.46	7.342%	$144.3321	$144.33	$144.35	$144.30
Purchase #2	$71.63	9.791%	$78.6433	$78.64	$78.65	$78.60
Purchase #3	$6.37	6.502%	$6.7842	$6.78	$6.80	$6.80
Purchase #4	$46.40	3.669%	$48.1024	$48.10	$48.10	$48.10
Purchase #5	$233.41	9.457%	$255.4836	$255.48	$255.50	$255.50
Purchase #6	$141.54	4.575%	$148.0155	$148.02	$148.00	$148.00
Purchase #7	$166.54	9.694%	$182.6844	$182.68	$182.70	$182.70
7 purchase totals =	$800.35		$864.0455	$864.03	$864.10	$864.00