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	$86.69	4.209%	$90.3388	$90.34	$90.35	$90.30
Purchase #2	$212.30	5.734%	$224.4733	$224.47	$224.45	$224.50
Purchase #3	$181.46	13.783%	$206.4706	$206.47	$206.45	$206.50
Purchase #4	$228.90	11.467%	$255.148	$255.15	$255.15	$255.10
Purchase #5	$177.77	6.621%	$189.5402	$189.54	$189.55	$189.50
Purchase #6	$204.67	10.310%	$225.7715	$225.77	$225.75	$225.80
Purchase #7	$242.68	13.467%	$275.3617	$275.36	$275.35	$275.40
7 purchase totals =	$1,334.47		$1,467.1041	$1,467.10	$1,467.05	$1,467.10