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	$220.69	5.558%	$232.956	$232.96	$232.95	$233.00
Purchase #2	$175.86	11.186%	$195.5317	$195.53	$195.55	$195.50
Purchase #3	$135.72	10.614%	$150.1253	$150.13	$150.15	$150.10
Purchase #4	$80.81	11.170%	$89.8365	$89.84	$89.85	$89.80
Purchase #5	$197.84	13.111%	$223.7788	$223.78	$223.80	$223.80
Purchase #6	$52.78	3.292%	$54.5175	$54.52	$54.50	$54.50
Purchase #7	$164.75	4.795%	$172.6498	$172.65	$172.65	$172.60
7 purchase totals =	$1,028.45		$1,119.3956	$1,119.41	$1,119.45	$1,119.30