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	$98.66	5.292%	$103.8811	$103.88	$103.90	$103.90
Purchase #2	$92.42	13.667%	$105.051	$105.05	$105.05	$105.10
Purchase #3	$237.54	4.185%	$247.481	$247.48	$247.50	$247.50
Purchase #4	$46.55	12.539%	$52.3869	$52.39	$52.40	$52.40
Purchase #5	$93.94	4.373%	$98.048	$98.05	$98.05	$98.00
Purchase #6	$29.80	8.493%	$32.3309	$32.33	$32.35	$32.30
Purchase #7	$94.60	4.482%	$98.84	$98.84	$98.85	$98.80
7 purchase totals =	$693.51		$738.0189	$738.02	$738.10	$738.00