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	$164.63	6.580%	$175.4627	$175.46	$175.45	$175.50
Purchase #2	$230.54	6.658%	$245.8894	$245.89	$245.90	$245.90
Purchase #3	$20.52	6.761%	$21.9074	$21.91	$21.90	$21.90
Purchase #4	$28.92	12.229%	$32.4566	$32.46	$32.45	$32.50
Purchase #5	$202.42	7.123%	$216.8384	$216.84	$216.85	$216.80
Purchase #6	$47.73	13.469%	$54.1588	$54.16	$54.15	$54.20
Purchase #7	$72.27	7.850%	$77.9432	$77.94	$77.95	$77.90
7 purchase totals =	$767.03		$824.6565	$824.66	$824.65	$824.70