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	$110.61	5.171%	$116.3296	$116.33	$116.35	$116.30
Purchase #2	$153.39	13.337%	$173.8476	$173.85	$173.85	$173.80
Purchase #3	$84.60	6.417%	$90.0288	$90.03	$90.05	$90.00
Purchase #4	$131.65	6.705%	$140.4771	$140.48	$140.50	$140.50
Purchase #5	$157.40	10.319%	$173.6421	$173.64	$173.65	$173.60
Purchase #6	$183.97	8.468%	$199.5486	$199.55	$199.55	$199.50
Purchase #7	$159.40	13.765%	$181.3414	$181.34	$181.35	$181.30
7 purchase totals =	$981.02		$1,075.2152	$1,075.22	$1,075.30	$1,075.00