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	$64.62	12.525%	$72.7137	$72.71	$72.70	$72.70
Purchase #2	$71.62	6.528%	$76.2954	$76.30	$76.30	$76.30
Purchase #3	$83.97	6.487%	$89.4171	$89.42	$89.40	$89.40
Purchase #4	$129.52	4.781%	$135.7124	$135.71	$135.70	$135.70
Purchase #5	$209.27	9.373%	$228.8849	$228.88	$228.90	$228.90
Purchase #6	$70.63	10.680%	$78.1733	$78.17	$78.15	$78.20
Purchase #7	$185.28	7.794%	$199.7207	$199.72	$199.70	$199.70
7 purchase totals =	$814.91		$880.9175	$880.91	$880.85	$880.90