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	$77.70	7.740%	$83.714	$83.71	$83.70	$83.70
Purchase #2	$54.63	5.292%	$57.521	$57.52	$57.50	$57.50
Purchase #3	$110.71	8.245%	$119.838	$119.84	$119.85	$119.80
Purchase #4	$103.47	7.864%	$111.6069	$111.61	$111.60	$111.60
Purchase #5	$160.89	12.534%	$181.056	$181.06	$181.05	$181.10
Purchase #6	$182.65	6.520%	$194.5588	$194.56	$194.55	$194.60
Purchase #7	$60.92	3.197%	$62.8676	$62.87	$62.85	$62.90
7 purchase totals =	$750.97		$811.1623	$811.17	$811.10	$811.20