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	$224.36	8.815%	$244.1373	$244.14	$244.15	$244.10
Purchase #2	$49.43	7.302%	$53.0394	$53.04	$53.05	$53.00
Purchase #3	$117.40	9.825%	$128.9346	$128.93	$128.95	$128.90
Purchase #4	$52.46	4.621%	$54.8842	$54.88	$54.90	$54.90
Purchase #5	$90.55	12.527%	$101.8932	$101.89	$101.90	$101.90
Purchase #6	$110.92	13.820%	$126.2491	$126.25	$126.25	$126.20
Purchase #7	$225.86	12.592%	$254.3003	$254.30	$254.30	$254.30
7 purchase totals =	$870.98		$963.4381	$963.43	$963.50	$963.30