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	$81.72	4.802%	$85.6442	$85.64	$85.65	$85.60
Purchase #2	$241.77	9.818%	$265.507	$265.51	$265.50	$265.50
Purchase #3	$23.46	12.199%	$26.3219	$26.32	$26.30	$26.30
Purchase #4	$54.32	10.178%	$59.8487	$59.85	$59.85	$59.80
Purchase #5	$244.53	7.789%	$263.5764	$263.58	$263.60	$263.60
Purchase #6	$240.30	3.654%	$249.0806	$249.08	$249.10	$249.10
Purchase #7	$140.81	7.603%	$151.5158	$151.52	$151.50	$151.50
7 purchase totals =	$1,026.91		$1,101.4946	$1,101.50	$1,101.50	$1,101.40