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	$156.42	6.274%	$166.2338	$166.23	$166.25	$166.20
Purchase #2	$107.87	11.745%	$120.5393	$120.54	$120.55	$120.50
Purchase #3	$235.48	10.790%	$260.8883	$260.89	$260.90	$260.90
Purchase #4	$72.25	8.303%	$78.2489	$78.25	$78.25	$78.20
Purchase #5	$113.61	8.592%	$123.3714	$123.37	$123.35	$123.40
Purchase #6	$116.71	8.123%	$126.1904	$126.19	$126.20	$126.20
Purchase #7	$212.37	7.773%	$228.8775	$228.88	$228.90	$228.90
7 purchase totals =	$1,014.71		$1,104.3496	$1,104.35	$1,104.40	$1,104.30