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	$182.43	7.748%	$196.5647	$196.56	$196.55	$196.60
Purchase #2	$84.56	9.167%	$92.3116	$92.31	$92.30	$92.30
Purchase #3	$165.51	12.483%	$186.1706	$186.17	$186.15	$186.20
Purchase #4	$138.54	6.337%	$147.3193	$147.32	$147.30	$147.30
Purchase #5	$247.96	10.775%	$274.6777	$274.68	$274.70	$274.70
Purchase #6	$52.55	12.523%	$59.1308	$59.13	$59.15	$59.10
Purchase #7	$202.28	8.819%	$220.1191	$220.12	$220.10	$220.10
7 purchase totals =	$1,073.83		$1,176.2938	$1,176.29	$1,176.25	$1,176.30