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	$90.79	7.386%	$97.4957	$97.50	$97.50	$97.50
Purchase #2	$248.94	4.392%	$259.8734	$259.87	$259.85	$259.90
Purchase #3	$198.32	7.384%	$212.9639	$212.96	$212.95	$213.00
Purchase #4	$78.74	12.528%	$88.6045	$88.60	$88.60	$88.60
Purchase #5	$152.93	12.572%	$172.1564	$172.16	$172.15	$172.20
Purchase #6	$122.80	6.388%	$130.6445	$130.64	$130.65	$130.60
Purchase #7	$81.73	4.530%	$85.4324	$85.43	$85.45	$85.40
7 purchase totals =	$974.25		$1,047.1708	$1,047.16	$1,047.15	$1,047.20