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	$100.51	9.386%	$109.9439	$109.94	$109.95	$109.90
Purchase #2	$121.44	7.308%	$130.3148	$130.31	$130.30	$130.30
Purchase #3	$136.59	12.375%	$153.493	$153.49	$153.50	$153.50
Purchase #4	$144.30	4.862%	$151.3159	$151.32	$151.30	$151.30
Purchase #5	$242.90	4.309%	$253.3666	$253.37	$253.35	$253.40
Purchase #6	$192.54	3.626%	$199.5215	$199.52	$199.50	$199.50
Purchase #7	$183.88	5.220%	$193.4785	$193.48	$193.50	$193.50
7 purchase totals =	$1,122.16		$1,191.4342	$1,191.43	$1,191.40	$1,191.40