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	$55.56	10.479%	$61.3821	$61.38	$61.40	$61.40
Purchase #2	$244.43	12.173%	$274.1845	$274.18	$274.20	$274.20
Purchase #3	$54.97	13.240%	$62.248	$62.25	$62.25	$62.20
Purchase #4	$46.92	7.493%	$50.4357	$50.44	$50.45	$50.40
Purchase #5	$149.31	6.737%	$159.369	$159.37	$159.35	$159.40
Purchase #6	$7.25	11.454%	$8.0804	$8.08	$8.10	$8.10
Purchase #7	$57.33	3.847%	$59.5355	$59.54	$59.55	$59.50
7 purchase totals =	$615.77		$675.2352	$675.24	$675.30	$675.20