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	$121.56	7.389%	$130.5421	$130.54	$130.55	$130.50
Purchase #2	$78.74	8.534%	$85.4597	$85.46	$85.45	$85.50
Purchase #3	$147.45	5.839%	$156.0596	$156.06	$156.05	$156.10
Purchase #4	$108.28	3.269%	$111.8197	$111.82	$111.80	$111.80
Purchase #5	$184.98	7.809%	$199.4251	$199.43	$199.45	$199.40
Purchase #6	$67.67	11.335%	$75.3404	$75.34	$75.35	$75.30
Purchase #7	$23.30	13.198%	$26.3751	$26.38	$26.40	$26.40
7 purchase totals =	$731.98		$785.0217	$785.03	$785.05	$785.00