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	$122.79	3.599%	$127.2092	$127.21	$127.20	$127.20
Purchase #2	$179.78	6.512%	$191.4873	$191.49	$191.50	$191.50
Purchase #3	$78.73	5.216%	$82.8366	$82.84	$82.85	$82.80
Purchase #4	$74.55	11.102%	$82.8265	$82.83	$82.85	$82.80
Purchase #5	$174.92	6.532%	$186.3458	$186.35	$186.35	$186.30
Purchase #6	$139.81	7.259%	$149.9588	$149.96	$149.95	$150.00
Purchase #7	$192.63	12.384%	$216.4853	$216.49	$216.50	$216.50
7 purchase totals =	$963.21		$1,037.1495	$1,037.17	$1,037.20	$1,037.10