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	$72.61	3.547%	$75.1855	$75.19	$75.20	$75.20
Purchase #2	$145.88	3.356%	$150.7757	$150.78	$150.80	$150.80
Purchase #3	$247.57	3.159%	$255.3907	$255.39	$255.40	$255.40
Purchase #4	$139.73	6.550%	$148.8823	$148.88	$148.90	$148.90
Purchase #5	$216.66	11.260%	$241.0559	$241.06	$241.05	$241.10
Purchase #6	$47.54	6.517%	$50.6382	$50.64	$50.65	$50.60
Purchase #7	$47.52	12.480%	$53.4505	$53.45	$53.45	$53.50
7 purchase totals =	$917.51		$975.3788	$975.39	$975.45	$975.50