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	$200.56	10.870%	$222.3609	$222.36	$222.35	$222.40
Purchase #2	$52.31	10.642%	$57.8768	$57.88	$57.90	$57.90
Purchase #3	$24.79	11.569%	$27.658	$27.66	$27.65	$27.70
Purchase #4	$38.67	6.776%	$41.2903	$41.29	$41.30	$41.30
Purchase #5	$25.82	9.167%	$28.1869	$28.19	$28.20	$28.20
Purchase #6	$51.41	11.294%	$57.2162	$57.22	$57.20	$57.20
Purchase #7	$158.51	5.797%	$167.6988	$167.70	$167.70	$167.70
7 purchase totals =	$552.07		$602.2879	$602.30	$602.30	$602.40