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	$66.34	7.576%	$71.3659	$71.37	$71.35	$71.40
Purchase #2	$245.82	11.818%	$274.871	$274.87	$274.85	$274.90
Purchase #3	$74.79	13.677%	$85.019	$85.02	$85.00	$85.00
Purchase #4	$181.84	3.576%	$188.3426	$188.34	$188.35	$188.30
Purchase #5	$114.71	7.681%	$123.5209	$123.52	$123.50	$123.50
Purchase #6	$83.25	12.742%	$93.8577	$93.86	$93.85	$93.90
Purchase #7	$216.43	9.816%	$237.6748	$237.67	$237.65	$237.70
7 purchase totals =	$983.18		$1,074.6519	$1,074.65	$1,074.55	$1,074.70