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	$247.32	12.134%	$277.3298	$277.33	$277.35	$277.30
Purchase #2	$196.69	13.641%	$223.5205	$223.52	$223.50	$223.50
Purchase #3	$37.89	4.708%	$39.6739	$39.67	$39.65	$39.70
Purchase #4	$27.89	5.127%	$29.3199	$29.32	$29.30	$29.30
Purchase #5	$100.46	5.463%	$105.9481	$105.95	$105.95	$105.90
Purchase #6	$177.95	11.435%	$198.2986	$198.30	$198.30	$198.30
Purchase #7	$69.98	11.672%	$78.1481	$78.15	$78.15	$78.10
7 purchase totals =	$858.18		$952.2389	$952.24	$952.20	$952.10