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	$141.48	6.669%	$150.9153	$150.92	$150.90	$150.90
Purchase #2	$118.40	11.160%	$131.6134	$131.61	$131.60	$131.60
Purchase #3	$240.54	8.391%	$260.7237	$260.72	$260.70	$260.70
Purchase #4	$204.81	4.312%	$213.6414	$213.64	$213.65	$213.60
Purchase #5	$226.71	12.414%	$254.8538	$254.85	$254.85	$254.90
Purchase #6	$41.82	8.330%	$45.3036	$45.30	$45.30	$45.30
Purchase #7	$117.57	8.388%	$127.4318	$127.43	$127.45	$127.40
7 purchase totals =	$1,091.33		$1,184.4830	$1,184.47	$1,184.45	$1,184.40