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	$133.72	13.257%	$151.4473	$151.45	$151.45	$151.40
Purchase #2	$41.27	7.864%	$44.5155	$44.52	$44.50	$44.50
Purchase #3	$216.69	3.211%	$223.6479	$223.65	$223.65	$223.60
Purchase #4	$52.83	6.871%	$56.4599	$56.46	$56.45	$56.50
Purchase #5	$143.81	11.699%	$160.6343	$160.63	$160.65	$160.60
Purchase #6	$127.93	12.118%	$143.4326	$143.43	$143.45	$143.40
Purchase #7	$173.61	6.842%	$185.4884	$185.49	$185.50	$185.50
7 purchase totals =	$889.86		$965.6259	$965.63	$965.65	$965.50