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	$75.42	13.746%	$85.7872	$85.79	$85.80	$85.80
Purchase #2	$178.95	8.817%	$194.728	$194.73	$194.75	$194.70
Purchase #3	$162.31	7.500%	$174.4833	$174.48	$174.50	$174.50
Purchase #4	$53.78	10.638%	$59.5011	$59.50	$59.50	$59.50
Purchase #5	$175.44	10.672%	$194.163	$194.16	$194.15	$194.20
Purchase #6	$75.63	12.542%	$85.1155	$85.12	$85.10	$85.10
Purchase #7	$160.64	9.274%	$175.5378	$175.54	$175.55	$175.50
7 purchase totals =	$882.17		$969.3159	$969.32	$969.35	$969.30