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	$208.34	10.264%	$229.724	$229.72	$229.70	$229.70
Purchase #2	$239.25	11.524%	$266.8212	$266.82	$266.80	$266.80
Purchase #3	$71.30	13.403%	$80.8563	$80.86	$80.85	$80.90
Purchase #4	$50.73	5.224%	$53.3801	$53.38	$53.40	$53.40
Purchase #5	$76.46	4.393%	$79.8189	$79.82	$79.80	$79.80
Purchase #6	$46.53	13.695%	$52.9023	$52.90	$52.90	$52.90
Purchase #7	$178.85	5.674%	$188.9979	$189.00	$189.00	$189.00
7 purchase totals =	$871.46		$952.5007	$952.50	$952.45	$952.50