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	$59.56	9.257%	$65.0735	$65.07	$65.05	$65.10
Purchase #2	$153.76	3.705%	$159.4568	$159.46	$159.45	$159.50
Purchase #3	$65.45	9.180%	$71.4583	$71.46	$71.45	$71.50
Purchase #4	$96.69	10.195%	$106.5475	$106.55	$106.55	$106.50
Purchase #5	$241.88	13.617%	$274.8168	$274.82	$274.80	$274.80
Purchase #6	$155.44	12.580%	$174.9944	$174.99	$175.00	$175.00
Purchase #7	$123.94	5.228%	$130.4196	$130.42	$130.40	$130.40
7 purchase totals =	$896.72		$982.7669	$982.77	$982.70	$982.80