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	$116.52	9.420%	$127.4962	$127.50	$127.50	$127.50
Purchase #2	$49.66	10.345%	$54.7973	$54.80	$54.80	$54.80
Purchase #3	$215.28	5.834%	$227.8394	$227.84	$227.85	$227.80
Purchase #4	$169.49	9.711%	$185.9492	$185.95	$185.95	$185.90
Purchase #5	$237.70	10.155%	$261.8384	$261.84	$261.85	$261.80
Purchase #6	$142.53	4.646%	$149.1519	$149.15	$149.15	$149.20
Purchase #7	$147.50	5.643%	$155.8234	$155.82	$155.80	$155.80
7 purchase totals =	$1,078.68		$1,162.8958	$1,162.90	$1,162.90	$1,162.80