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	$195.25	12.370%	$219.4024	$219.40	$219.40	$219.40
Purchase #2	$180.51	5.535%	$190.5012	$190.50	$190.50	$190.50
Purchase #3	$92.75	8.130%	$100.2906	$100.29	$100.30	$100.30
Purchase #4	$183.46	5.407%	$193.3797	$193.38	$193.40	$193.40
Purchase #5	$134.41	8.613%	$145.9867	$145.99	$146.00	$146.00
Purchase #6	$145.95	13.145%	$165.1351	$165.14	$165.15	$165.10
Purchase #7	$82.79	3.549%	$85.7282	$85.73	$85.75	$85.70
7 purchase totals =	$1,015.12		$1,100.4239	$1,100.43	$1,100.50	$1,100.40