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	$41.88	5.285%	$44.0934	$44.09	$44.10	$44.10
Purchase #2	$26.38	4.377%	$27.5347	$27.53	$27.55	$27.50
Purchase #3	$81.34	11.733%	$90.8836	$90.88	$90.90	$90.90
Purchase #4	$85.50	11.176%	$95.0555	$95.06	$95.05	$95.10
Purchase #5	$42.82	4.593%	$44.7867	$44.79	$44.80	$44.80
Purchase #6	$227.27	3.461%	$235.1358	$235.14	$235.15	$235.10
Purchase #7	$99.95	13.275%	$113.2184	$113.22	$113.20	$113.20
7 purchase totals =	$605.14		$650.7081	$650.71	$650.75	$650.70