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	$213.54	11.391%	$237.8643	$237.86	$237.85	$237.90
Purchase #2	$54.73	13.794%	$62.2795	$62.28	$62.30	$62.30
Purchase #3	$47.54	12.137%	$53.3099	$53.31	$53.30	$53.30
Purchase #4	$93.86	13.759%	$106.7742	$106.77	$106.75	$106.80
Purchase #5	$143.64	11.819%	$160.6168	$160.62	$160.60	$160.60
Purchase #6	$147.95	7.541%	$159.1069	$159.11	$159.10	$159.10
Purchase #7	$81.40	10.439%	$89.8973	$89.90	$89.90	$89.90
7 purchase totals =	$782.66		$869.8489	$869.85	$869.80	$869.90