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	$207.44	6.761%	$221.465	$221.47	$221.45	$221.50
Purchase #2	$86.42	4.757%	$90.531	$90.53	$90.55	$90.50
Purchase #3	$61.31	5.482%	$64.671	$64.67	$64.65	$64.70
Purchase #4	$35.86	13.391%	$40.662	$40.66	$40.65	$40.70
Purchase #5	$6.64	12.308%	$7.4573	$7.46	$7.45	$7.50
Purchase #6	$128.25	6.640%	$136.7658	$136.77	$136.75	$136.80
Purchase #7	$155.74	7.656%	$167.6635	$167.66	$167.65	$167.70
7 purchase totals =	$681.66		$729.2156	$729.22	$729.15	$729.40