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	$126.27	6.604%	$134.6089	$134.61	$134.60	$134.60
Purchase #2	$179.46	6.773%	$191.6148	$191.61	$191.60	$191.60
Purchase #3	$110.53	8.778%	$120.2323	$120.23	$120.25	$120.20
Purchase #4	$243.93	13.763%	$277.5021	$277.50	$277.50	$277.50
Purchase #5	$33.61	11.852%	$37.5935	$37.59	$37.60	$37.60
Purchase #6	$249.80	12.226%	$280.3405	$280.34	$280.35	$280.30
Purchase #7	$163.27	3.597%	$169.1428	$169.14	$169.15	$169.10
7 purchase totals =	$1,106.87		$1,211.0349	$1,211.02	$1,211.05	$1,210.90