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	$126.43	4.212%	$131.7552	$131.76	$131.75	$131.80
Purchase #2	$55.96	11.706%	$62.5107	$62.51	$62.50	$62.50
Purchase #3	$89.95	10.299%	$99.214	$99.21	$99.20	$99.20
Purchase #4	$20.84	8.122%	$22.5326	$22.53	$22.55	$22.50
Purchase #5	$43.57	10.361%	$48.0843	$48.08	$48.10	$48.10
Purchase #6	$39.30	9.608%	$43.0759	$43.08	$43.10	$43.10
Purchase #7	$23.77	12.653%	$26.7776	$26.78	$26.80	$26.80
7 purchase totals =	$399.82		$433.9503	$433.95	$434.00	$434.00