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	$190.88	4.712%	$199.8743	$199.87	$199.85	$199.90
Purchase #2	$41.62	5.353%	$43.8479	$43.85	$43.85	$43.80
Purchase #3	$51.89	3.782%	$53.8525	$53.85	$53.85	$53.90
Purchase #4	$243.63	11.242%	$271.0189	$271.02	$271.00	$271.00
Purchase #5	$68.33	13.839%	$77.7862	$77.79	$77.80	$77.80
Purchase #6	$44.83	3.636%	$46.46	$46.46	$46.45	$46.50
Purchase #7	$211.45	5.620%	$223.3335	$223.33	$223.35	$223.30
7 purchase totals =	$852.63		$916.1733	$916.17	$916.15	$916.20