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	$57.69	5.749%	$61.0066	$61.01	$61.00	$61.00
Purchase #2	$60.96	4.323%	$63.5953	$63.60	$63.60	$63.60
Purchase #3	$65.98	10.554%	$72.9435	$72.94	$72.95	$72.90
Purchase #4	$196.49	10.398%	$216.921	$216.92	$216.90	$216.90
Purchase #5	$238.75	12.839%	$269.4031	$269.40	$269.40	$269.40
Purchase #6	$156.84	8.159%	$169.6366	$169.64	$169.65	$169.60
Purchase #7	$203.74	13.240%	$230.7152	$230.72	$230.70	$230.70
7 purchase totals =	$980.45		$1,084.2213	$1,084.23	$1,084.20	$1,084.10