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	$208.88	12.814%	$235.6459	$235.65	$235.65	$235.60
Purchase #2	$43.43	4.143%	$45.2293	$45.23	$45.25	$45.20
Purchase #3	$197.77	7.611%	$212.8223	$212.82	$212.80	$212.80
Purchase #4	$105.62	6.517%	$112.5033	$112.50	$112.50	$112.50
Purchase #5	$34.99	6.407%	$37.2318	$37.23	$37.25	$37.20
Purchase #6	$177.47	7.539%	$190.8495	$190.85	$190.85	$190.80
Purchase #7	$83.30	13.301%	$94.3797	$94.38	$94.40	$94.40
7 purchase totals =	$851.46		$928.6618	$928.66	$928.70	$928.50