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	$92.96	13.819%	$105.8061	$105.81	$105.80	$105.80
Purchase #2	$90.72	10.452%	$100.2021	$100.20	$100.20	$100.20
Purchase #3	$233.32	4.564%	$243.9687	$243.97	$243.95	$244.00
Purchase #4	$64.60	10.814%	$71.5858	$71.59	$71.60	$71.60
Purchase #5	$105.48	6.352%	$112.1801	$112.18	$112.20	$112.20
Purchase #6	$218.37	3.542%	$226.1047	$226.10	$226.10	$226.10
Purchase #7	$234.85	4.542%	$245.5169	$245.52	$245.50	$245.50
7 purchase totals =	$1,040.30		$1,105.3644	$1,105.37	$1,105.35	$1,105.40