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	$17.60	10.801%	$19.501	$19.50	$19.50	$19.50
Purchase #2	$119.89	12.203%	$134.5202	$134.52	$134.50	$134.50
Purchase #3	$200.40	6.297%	$213.0192	$213.02	$213.00	$213.00
Purchase #4	$138.41	7.484%	$148.7686	$148.77	$148.75	$148.80
Purchase #5	$243.73	13.810%	$277.3891	$277.39	$277.40	$277.40
Purchase #6	$33.75	9.755%	$37.0423	$37.04	$37.05	$37.00
Purchase #7	$161.74	6.386%	$172.0687	$172.07	$172.05	$172.10
7 purchase totals =	$915.52		$1,002.3091	$1,002.31	$1,002.25	$1,002.30