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	$174.85	5.863%	$185.1015	$185.10	$185.10	$185.10
Purchase #2	$163.66	9.283%	$178.8526	$178.85	$178.85	$178.90
Purchase #3	$177.34	6.275%	$188.4681	$188.47	$188.45	$188.50
Purchase #4	$95.50	11.813%	$106.7814	$106.78	$106.80	$106.80
Purchase #5	$55.96	11.519%	$62.406	$62.41	$62.40	$62.40
Purchase #6	$230.89	3.644%	$239.3036	$239.30	$239.30	$239.30
Purchase #7	$114.33	9.733%	$125.4577	$125.46	$125.45	$125.50
7 purchase totals =	$1,012.53		$1,086.3709	$1,086.37	$1,086.35	$1,086.50