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	$116.27	12.544%	$130.8549	$130.85	$130.85	$130.90
Purchase #2	$140.87	10.264%	$155.3289	$155.33	$155.35	$155.30
Purchase #3	$86.61	10.611%	$95.8002	$95.80	$95.80	$95.80
Purchase #4	$217.45	6.326%	$231.2059	$231.21	$231.20	$231.20
Purchase #5	$237.73	3.251%	$245.4586	$245.46	$245.45	$245.50
Purchase #6	$239.78	10.296%	$264.4677	$264.47	$264.45	$264.50
Purchase #7	$40.45	13.357%	$45.8529	$45.85	$45.85	$45.90
7 purchase totals =	$1,079.16		$1,168.9691	$1,168.97	$1,168.95	$1,169.10