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	$171.60	8.315%	$185.8685	$185.87	$185.85	$185.90
Purchase #2	$185.37	5.870%	$196.2512	$196.25	$196.25	$196.30
Purchase #3	$80.44	3.749%	$83.4557	$83.46	$83.45	$83.50
Purchase #4	$17.76	5.830%	$18.7954	$18.80	$18.80	$18.80
Purchase #5	$177.29	7.263%	$190.1666	$190.17	$190.15	$190.20
Purchase #6	$205.50	13.580%	$233.4069	$233.41	$233.40	$233.40
Purchase #7	$60.81	11.499%	$67.8025	$67.80	$67.80	$67.80
7 purchase totals =	$898.77		$975.7468	$975.76	$975.70	$975.90