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	$35.81	4.409%	$37.3889	$37.39	$37.40	$37.40
Purchase #2	$134.52	11.686%	$150.24	$150.24	$150.25	$150.20
Purchase #3	$61.30	12.453%	$68.9337	$68.93	$68.95	$68.90
Purchase #4	$95.35	4.339%	$99.4872	$99.49	$99.50	$99.50
Purchase #5	$59.72	12.505%	$67.188	$67.19	$67.20	$67.20
Purchase #6	$181.52	8.356%	$196.6878	$196.69	$196.70	$196.70
Purchase #7	$98.74	4.579%	$103.2613	$103.26	$103.25	$103.30
7 purchase totals =	$666.96		$723.1869	$723.19	$723.25	$723.20