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	$190.63	11.769%	$213.0652	$213.07	$213.05	$213.10
Purchase #2	$78.87	11.629%	$88.0418	$88.04	$88.05	$88.00
Purchase #3	$148.46	11.495%	$165.5255	$165.53	$165.55	$165.50
Purchase #4	$176.58	8.195%	$191.0507	$191.05	$191.05	$191.10
Purchase #5	$142.47	6.284%	$151.4228	$151.42	$151.40	$151.40
Purchase #6	$174.45	9.204%	$190.5064	$190.51	$190.50	$190.50
Purchase #7	$217.42	5.753%	$229.9282	$229.93	$229.95	$229.90
7 purchase totals =	$1,128.88		$1,229.5406	$1,229.55	$1,229.55	$1,229.50