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	$129.37	10.175%	$142.5334	$142.53	$142.55	$142.50
Purchase #2	$29.45	10.471%	$32.5337	$32.53	$32.55	$32.50
Purchase #3	$141.46	7.286%	$151.7668	$151.77	$151.75	$151.80
Purchase #4	$187.49	11.226%	$208.5376	$208.54	$208.55	$208.50
Purchase #5	$245.51	9.808%	$269.5896	$269.59	$269.60	$269.60
Purchase #6	$130.42	4.148%	$135.8298	$135.83	$135.85	$135.80
Purchase #7	$202.91	3.259%	$209.5228	$209.52	$209.50	$209.50
7 purchase totals =	$1,066.61		$1,150.3137	$1,150.31	$1,150.35	$1,150.20