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	$209.73	9.581%	$229.8242	$229.82	$229.80	$229.80
Purchase #2	$129.39	6.376%	$137.6399	$137.64	$137.65	$137.60
Purchase #3	$12.48	5.612%	$13.1804	$13.18	$13.20	$13.20
Purchase #4	$228.88	5.658%	$241.83	$241.83	$241.85	$241.80
Purchase #5	$116.80	11.399%	$130.114	$130.11	$130.10	$130.10
Purchase #6	$38.69	4.599%	$40.4694	$40.47	$40.45	$40.50
Purchase #7	$54.44	8.448%	$59.0391	$59.04	$59.05	$59.00
7 purchase totals =	$790.41		$852.0970	$852.09	$852.10	$852.00