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	$207.85	11.306%	$231.3495	$231.35	$231.35	$231.30
Purchase #2	$168.27	10.649%	$186.1891	$186.19	$186.20	$186.20
Purchase #3	$224.32	13.734%	$255.1281	$255.13	$255.15	$255.10
Purchase #4	$107.63	3.791%	$111.7103	$111.71	$111.70	$111.70
Purchase #5	$135.32	12.193%	$151.8196	$151.82	$151.80	$151.80
Purchase #6	$35.30	6.770%	$37.6898	$37.69	$37.70	$37.70
Purchase #7	$53.59	13.465%	$60.8059	$60.81	$60.80	$60.80
7 purchase totals =	$932.28		$1,034.6923	$1,034.70	$1,034.70	$1,034.60