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	$101.40	3.362%	$104.8091	$104.81	$104.80	$104.80
Purchase #2	$180.55	5.234%	$190	$190.00	$190.00	$190.00
Purchase #3	$190.86	7.390%	$204.9646	$204.96	$204.95	$205.00
Purchase #4	$144.85	8.251%	$156.8016	$156.80	$156.80	$156.80
Purchase #5	$207.27	6.763%	$221.2877	$221.29	$221.30	$221.30
Purchase #6	$41.58	8.356%	$45.0544	$45.05	$45.05	$45.10
Purchase #7	$137.33	9.591%	$150.5013	$150.50	$150.50	$150.50
7 purchase totals =	$1,003.84		$1,073.4187	$1,073.41	$1,073.40	$1,073.50