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	$90.95	10.452%	$100.4561	$100.46	$100.45	$100.50
Purchase #2	$116.40	11.288%	$129.5392	$129.54	$129.55	$129.50
Purchase #3	$33.52	4.552%	$35.0458	$35.05	$35.05	$35.00
Purchase #4	$107.72	10.730%	$119.2784	$119.28	$119.30	$119.30
Purchase #5	$178.35	11.419%	$198.7158	$198.72	$198.70	$198.70
Purchase #6	$22.35	7.184%	$23.9556	$23.96	$23.95	$24.00
Purchase #7	$80.99	11.659%	$90.4326	$90.43	$90.45	$90.40
7 purchase totals =	$630.28		$697.4235	$697.44	$697.45	$697.40