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	$39.61	4.135%	$41.2479	$41.25	$41.25	$41.20
Purchase #2	$114.63	13.648%	$130.2747	$130.27	$130.25	$130.30
Purchase #3	$224.27	12.186%	$251.5995	$251.60	$251.60	$251.60
Purchase #4	$171.98	11.484%	$191.7302	$191.73	$191.75	$191.70
Purchase #5	$150.42	4.493%	$157.1784	$157.18	$157.20	$157.20
Purchase #6	$133.68	7.391%	$143.5603	$143.56	$143.55	$143.60
Purchase #7	$71.55	10.334%	$78.944	$78.94	$78.95	$78.90
7 purchase totals =	$906.14		$994.5350	$994.53	$994.55	$994.50