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	$188.56	4.869%	$197.741	$197.74	$197.75	$197.70
Purchase #2	$188.51	9.483%	$206.3864	$206.39	$206.40	$206.40
Purchase #3	$237.50	5.649%	$250.9164	$250.92	$250.90	$250.90
Purchase #4	$161.64	6.746%	$172.5442	$172.54	$172.55	$172.50
Purchase #5	$6.53	11.538%	$7.2834	$7.28	$7.30	$7.30
Purchase #6	$118.47	4.148%	$123.3841	$123.38	$123.40	$123.40
Purchase #7	$240.33	7.373%	$258.0495	$258.05	$258.05	$258.00
7 purchase totals =	$1,141.54		$1,216.3050	$1,216.30	$1,216.35	$1,216.20