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	$156.30	8.620%	$169.7731	$169.77	$169.75	$169.80
Purchase #2	$182.82	7.654%	$196.813	$196.81	$196.80	$196.80
Purchase #3	$173.29	6.473%	$184.5071	$184.51	$184.50	$184.50
Purchase #4	$83.83	13.849%	$95.4396	$95.44	$95.45	$95.40
Purchase #5	$86.65	11.468%	$96.587	$96.59	$96.60	$96.60
Purchase #6	$71.57	6.215%	$76.0181	$76.02	$76.00	$76.00
Purchase #7	$247.37	12.367%	$277.9622	$277.96	$277.95	$278.00
7 purchase totals =	$1,001.83		$1,097.1001	$1,097.10	$1,097.05	$1,097.10