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	$125.62	11.500%	$140.0663	$140.07	$140.05	$140.10
Purchase #2	$40.39	3.793%	$41.922	$41.92	$41.90	$41.90
Purchase #3	$173.89	6.594%	$185.3563	$185.36	$185.35	$185.40
Purchase #4	$33.74	13.765%	$38.3843	$38.38	$38.40	$38.40
Purchase #5	$58.55	6.397%	$62.2954	$62.30	$62.30	$62.30
Purchase #6	$59.29	13.423%	$67.2485	$67.25	$67.25	$67.20
Purchase #7	$23.31	11.215%	$25.9242	$25.92	$25.90	$25.90
7 purchase totals =	$514.79		$561.1970	$561.20	$561.15	$561.20