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	$87.40	8.871%	$95.1533	$95.15	$95.15	$95.20
Purchase #2	$159.51	13.562%	$181.1427	$181.14	$181.15	$181.10
Purchase #3	$149.58	4.636%	$156.5145	$156.51	$156.50	$156.50
Purchase #4	$121.44	6.183%	$128.9486	$128.95	$128.95	$128.90
Purchase #5	$191.51	7.360%	$205.6051	$205.61	$205.60	$205.60
Purchase #6	$145.77	7.552%	$156.7786	$156.78	$156.80	$156.80
Purchase #7	$90.60	8.465%	$98.2693	$98.27	$98.25	$98.30
7 purchase totals =	$945.81		$1,022.4121	$1,022.41	$1,022.40	$1,022.40