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	$106.99	3.524%	$110.7603	$110.76	$110.75	$110.80
Purchase #2	$244.87	12.624%	$275.7824	$275.78	$275.80	$275.80
Purchase #3	$91.30	13.658%	$103.7698	$103.77	$103.75	$103.80
Purchase #4	$38.52	10.175%	$42.4394	$42.44	$42.45	$42.40
Purchase #5	$127.48	13.597%	$144.8135	$144.81	$144.80	$144.80
Purchase #6	$141.98	3.663%	$147.1807	$147.18	$147.20	$147.20
Purchase #7	$102.65	13.513%	$116.5211	$116.52	$116.50	$116.50
7 purchase totals =	$853.79		$941.2672	$941.26	$941.25	$941.30