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	$157.93	8.346%	$171.1108	$171.11	$171.10	$171.10
Purchase #2	$72.92	13.166%	$82.5206	$82.52	$82.50	$82.50
Purchase #3	$14.48	8.484%	$15.7085	$15.71	$15.70	$15.70
Purchase #4	$138.60	9.385%	$151.6076	$151.61	$151.60	$151.60
Purchase #5	$175.99	13.349%	$199.4829	$199.48	$199.50	$199.50
Purchase #6	$156.38	12.163%	$175.4005	$175.40	$175.40	$175.40
Purchase #7	$185.89	10.491%	$205.3917	$205.39	$205.40	$205.40
7 purchase totals =	$902.19		$1,001.2226	$1,001.22	$1,001.20	$1,001.20