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	$193.48	6.675%	$206.3948	$206.39	$206.40	$206.40
Purchase #2	$174.96	12.473%	$196.7828	$196.78	$196.80	$196.80
Purchase #3	$56.46	8.721%	$61.3839	$61.38	$61.40	$61.40
Purchase #4	$152.31	6.385%	$162.035	$162.04	$162.05	$162.00
Purchase #5	$20.69	7.640%	$22.2707	$22.27	$22.25	$22.30
Purchase #6	$23.82	10.558%	$26.3349	$26.33	$26.35	$26.30
Purchase #7	$147.60	7.388%	$158.5047	$158.50	$158.50	$158.50
7 purchase totals =	$769.32		$833.7068	$833.69	$833.75	$833.70