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	$82.30	7.307%	$88.3137	$88.31	$88.30	$88.30
Purchase #2	$89.89	11.248%	$100.0008	$100.00	$100.00	$100.00
Purchase #3	$187.69	9.488%	$205.498	$205.50	$205.50	$205.50
Purchase #4	$68.82	3.606%	$71.3016	$71.30	$71.30	$71.30
Purchase #5	$154.90	4.631%	$162.0734	$162.07	$162.05	$162.10
Purchase #6	$148.42	7.442%	$159.4654	$159.47	$159.45	$159.50
Purchase #7	$166.61	9.135%	$181.8298	$181.83	$181.85	$181.80
7 purchase totals =	$898.63		$968.4827	$968.48	$968.45	$968.50