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	$226.29	3.302%	$233.7621	$233.76	$233.75	$233.80
Purchase #2	$222.27	8.336%	$240.7984	$240.80	$240.80	$240.80
Purchase #3	$40.72	10.823%	$45.1271	$45.13	$45.15	$45.10
Purchase #4	$183.64	7.193%	$196.8492	$196.85	$196.85	$196.80
Purchase #5	$81.51	8.313%	$88.2859	$88.29	$88.30	$88.30
Purchase #6	$93.43	5.224%	$98.3108	$98.31	$98.30	$98.30
Purchase #7	$6.63	11.715%	$7.4067	$7.41	$7.40	$7.40
7 purchase totals =	$854.49		$910.5402	$910.55	$910.55	$910.50