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	$73.56	7.213%	$78.8659	$78.87	$78.85	$78.90
Purchase #2	$110.56	7.470%	$118.8188	$118.82	$118.80	$118.80
Purchase #3	$169.97	5.549%	$179.4016	$179.40	$179.40	$179.40
Purchase #4	$189.62	8.377%	$205.5045	$205.50	$205.50	$205.50
Purchase #5	$223.83	4.545%	$234.0031	$234.00	$234.00	$234.00
Purchase #6	$81.38	8.696%	$88.4568	$88.46	$88.45	$88.50
Purchase #7	$97.31	8.705%	$105.7808	$105.78	$105.80	$105.80
7 purchase totals =	$946.23		$1,010.8315	$1,010.83	$1,010.80	$1,010.90