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	$64.38	9.869%	$70.7337	$70.73	$70.75	$70.70
Purchase #2	$104.39	7.114%	$111.8163	$111.82	$111.80	$111.80
Purchase #3	$83.51	10.734%	$92.474	$92.47	$92.45	$92.50
Purchase #4	$216.69	7.420%	$232.7684	$232.77	$232.75	$232.80
Purchase #5	$99.94	6.821%	$106.7569	$106.76	$106.75	$106.80
Purchase #6	$203.91	4.263%	$212.6027	$212.60	$212.60	$212.60
Purchase #7	$156.51	11.818%	$175.0064	$175.01	$175.00	$175.00
7 purchase totals =	$929.33		$1,002.1584	$1,002.16	$1,002.10	$1,002.20