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	$34.51	8.318%	$37.3805	$37.38	$37.40	$37.40
Purchase #2	$32.32	8.233%	$34.9809	$34.98	$35.00	$35.00
Purchase #3	$203.94	12.221%	$228.8635	$228.86	$228.85	$228.90
Purchase #4	$85.54	6.362%	$90.9821	$90.98	$91.00	$91.00
Purchase #5	$245.51	9.726%	$269.3883	$269.39	$269.40	$269.40
Purchase #6	$94.25	10.394%	$104.0463	$104.05	$104.05	$104.00
Purchase #7	$229.43	9.726%	$251.7444	$251.74	$251.75	$251.70
7 purchase totals =	$925.50		$1,017.3860	$1,017.38	$1,017.45	$1,017.40