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	$43.40	4.534%	$45.3678	$45.37	$45.35	$45.40
Purchase #2	$221.94	10.579%	$245.419	$245.42	$245.40	$245.40
Purchase #3	$72.48	8.194%	$78.419	$78.42	$78.40	$78.40
Purchase #4	$197.85	11.794%	$221.1844	$221.18	$221.20	$221.20
Purchase #5	$65.67	10.614%	$72.6402	$72.64	$72.65	$72.60
Purchase #6	$39.44	7.519%	$42.4055	$42.41	$42.40	$42.40
Purchase #7	$243.51	10.785%	$269.7726	$269.77	$269.75	$269.80
7 purchase totals =	$884.29		$975.2085	$975.21	$975.15	$975.20