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	$62.34	7.665%	$67.1184	$67.12	$67.10	$67.10
Purchase #2	$152.61	11.201%	$169.7038	$169.70	$169.70	$169.70
Purchase #3	$28.26	10.854%	$31.3273	$31.33	$31.35	$31.30
Purchase #4	$58.72	3.802%	$60.9525	$60.95	$60.95	$61.00
Purchase #5	$49.37	11.210%	$54.9044	$54.90	$54.90	$54.90
Purchase #6	$213.92	7.429%	$229.8121	$229.81	$229.80	$229.80
Purchase #7	$54.85	8.500%	$59.5123	$59.51	$59.50	$59.50
7 purchase totals =	$620.07		$673.3308	$673.32	$673.30	$673.30