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	$168.28	10.477%	$185.9107	$185.91	$185.90	$185.90
Purchase #2	$52.40	5.575%	$55.3213	$55.32	$55.30	$55.30
Purchase #3	$161.30	6.347%	$171.5377	$171.54	$171.55	$171.50
Purchase #4	$76.80	6.482%	$81.7782	$81.78	$81.80	$81.80
Purchase #5	$246.76	9.115%	$269.2522	$269.25	$269.25	$269.30
Purchase #6	$55.27	9.635%	$60.5953	$60.60	$60.60	$60.60
Purchase #7	$40.78	3.360%	$42.1502	$42.15	$42.15	$42.20
7 purchase totals =	$801.59		$866.5456	$866.55	$866.55	$866.60