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	$191.37	4.631%	$200.2323	$200.23	$200.25	$200.20
Purchase #2	$222.41	9.319%	$243.1364	$243.14	$243.15	$243.10
Purchase #3	$144.47	5.565%	$152.5098	$152.51	$152.50	$152.50
Purchase #4	$211.87	7.607%	$227.987	$227.99	$228.00	$228.00
Purchase #5	$121.25	8.665%	$131.7563	$131.76	$131.75	$131.80
Purchase #6	$66.51	7.706%	$71.6353	$71.64	$71.65	$71.60
Purchase #7	$187.79	4.780%	$196.7664	$196.77	$196.75	$196.80
7 purchase totals =	$1,145.67		$1,224.0235	$1,224.04	$1,224.05	$1,224.00