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	$223.55	3.521%	$231.4212	$231.42	$231.40	$231.40
Purchase #2	$219.67	6.286%	$233.4785	$233.48	$233.50	$233.50
Purchase #3	$101.62	12.467%	$114.289	$114.29	$114.30	$114.30
Purchase #4	$111.88	7.359%	$120.1132	$120.11	$120.10	$120.10
Purchase #5	$87.33	3.796%	$90.645	$90.65	$90.65	$90.60
Purchase #6	$48.94	4.248%	$51.019	$51.02	$51.00	$51.00
Purchase #7	$156.71	12.238%	$175.8882	$175.89	$175.90	$175.90
7 purchase totals =	$949.70		$1,016.8541	$1,016.86	$1,016.85	$1,016.80