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	$111.65	4.355%	$116.5124	$116.51	$116.50	$116.50
Purchase #2	$7.59	7.343%	$8.1473	$8.15	$8.15	$8.10
Purchase #3	$154.87	6.749%	$165.3222	$165.32	$165.30	$165.30
Purchase #4	$152.80	9.825%	$167.8126	$167.81	$167.80	$167.80
Purchase #5	$78.84	13.461%	$89.4527	$89.45	$89.45	$89.50
Purchase #6	$232.82	3.847%	$241.7766	$241.78	$241.80	$241.80
Purchase #7	$57.73	11.206%	$64.1992	$64.20	$64.20	$64.20
7 purchase totals =	$796.30		$853.2230	$853.22	$853.20	$853.20