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	$92.53	6.396%	$98.4482	$98.45	$98.45	$98.40
Purchase #2	$175.96	5.131%	$184.9885	$184.99	$185.00	$185.00
Purchase #3	$79.56	12.406%	$89.4302	$89.43	$89.45	$89.40
Purchase #4	$216.77	7.282%	$232.5552	$232.56	$232.55	$232.60
Purchase #5	$10.53	3.496%	$10.8981	$10.90	$10.90	$10.90
Purchase #6	$96.76	7.174%	$103.7016	$103.70	$103.70	$103.70
Purchase #7	$225.77	5.607%	$238.4289	$238.43	$238.45	$238.40
7 purchase totals =	$897.88		$958.4507	$958.46	$958.50	$958.40