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	$86.57	12.181%	$97.1151	$97.12	$97.10	$97.10
Purchase #2	$163.72	3.388%	$169.2668	$169.27	$169.25	$169.30
Purchase #3	$119.67	12.335%	$134.4313	$134.43	$134.45	$134.40
Purchase #4	$79.25	3.867%	$82.3146	$82.31	$82.30	$82.30
Purchase #5	$6.31	8.733%	$6.8611	$6.86	$6.85	$6.90
Purchase #6	$80.77	5.807%	$85.4603	$85.46	$85.45	$85.50
Purchase #7	$205.57	13.681%	$233.694	$233.69	$233.70	$233.70
7 purchase totals =	$741.86		$809.1432	$809.14	$809.10	$809.20