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	$169.89	7.334%	$182.3497	$182.35	$182.35	$182.30
Purchase #2	$111.56	4.680%	$116.781	$116.78	$116.80	$116.80
Purchase #3	$47.61	11.372%	$53.0242	$53.02	$53.00	$53.00
Purchase #4	$152.38	12.456%	$171.3605	$171.36	$171.35	$171.40
Purchase #5	$95.25	11.736%	$106.4285	$106.43	$106.45	$106.40
Purchase #6	$136.26	13.438%	$154.5706	$154.57	$154.55	$154.60
Purchase #7	$228.81	9.549%	$250.6591	$250.66	$250.65	$250.70
7 purchase totals =	$941.76		$1,035.1736	$1,035.17	$1,035.15	$1,035.20