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	$192.38	12.708%	$216.8277	$216.83	$216.85	$216.80
Purchase #2	$43.82	11.215%	$48.7344	$48.73	$48.75	$48.70
Purchase #3	$79.95	3.369%	$82.6435	$82.64	$82.65	$82.60
Purchase #4	$165.62	8.536%	$179.7573	$179.76	$179.75	$179.80
Purchase #5	$12.30	4.331%	$12.8327	$12.83	$12.85	$12.80
Purchase #6	$225.93	8.765%	$245.7328	$245.73	$245.75	$245.70
Purchase #7	$221.90	4.297%	$231.435	$231.44	$231.45	$231.40
7 purchase totals =	$941.90		$1,017.9634	$1,017.96	$1,018.05	$1,017.80