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	$134.42	11.827%	$150.3179	$150.32	$150.30	$150.30
Purchase #2	$75.31	13.531%	$85.5002	$85.50	$85.50	$85.50
Purchase #3	$6.90	9.760%	$7.5734	$7.57	$7.55	$7.60
Purchase #4	$185.35	6.117%	$196.6879	$196.69	$196.70	$196.70
Purchase #5	$229.59	12.504%	$258.2979	$258.30	$258.30	$258.30
Purchase #6	$82.44	6.373%	$87.6939	$87.69	$87.70	$87.70
Purchase #7	$33.72	11.118%	$37.469	$37.47	$37.45	$37.50
7 purchase totals =	$747.73		$823.5402	$823.54	$823.50	$823.60