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	$195.99	12.558%	$220.6024	$220.60	$220.60	$220.60
Purchase #2	$232.56	8.209%	$251.6509	$251.65	$251.65	$251.70
Purchase #3	$100.77	3.625%	$104.4229	$104.42	$104.40	$104.40
Purchase #4	$95.80	4.823%	$100.4204	$100.42	$100.40	$100.40
Purchase #5	$93.43	4.261%	$97.4111	$97.41	$97.40	$97.40
Purchase #6	$80.89	13.526%	$91.8312	$91.83	$91.85	$91.80
Purchase #7	$96.78	13.498%	$109.8434	$109.84	$109.85	$109.80
7 purchase totals =	$896.22		$976.1823	$976.17	$976.15	$976.10