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	$208.54	11.802%	$233.1519	$233.15	$233.15	$233.20
Purchase #2	$171.64	7.601%	$184.6864	$184.69	$184.70	$184.70
Purchase #3	$160.48	11.327%	$178.6576	$178.66	$178.65	$178.70
Purchase #4	$237.30	5.287%	$249.8461	$249.85	$249.85	$249.80
Purchase #5	$209.82	6.396%	$223.2401	$223.24	$223.25	$223.20
Purchase #6	$250.77	12.763%	$282.7758	$282.78	$282.80	$282.80
Purchase #7	$40.82	7.593%	$43.9195	$43.92	$43.90	$43.90
7 purchase totals =	$1,279.37		$1,396.2774	$1,396.29	$1,396.30	$1,396.30