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	$100.81	8.650%	$109.5301	$109.53	$109.55	$109.50
Purchase #2	$140.41	11.673%	$156.8001	$156.80	$156.80	$156.80
Purchase #3	$85.69	11.396%	$95.4552	$95.46	$95.45	$95.50
Purchase #4	$48.67	10.839%	$53.9453	$53.95	$53.95	$53.90
Purchase #5	$28.77	12.812%	$32.456	$32.46	$32.45	$32.50
Purchase #6	$21.30	10.327%	$23.4997	$23.50	$23.50	$23.50
Purchase #7	$231.44	7.847%	$249.6011	$249.60	$249.60	$249.60
7 purchase totals =	$657.09		$721.2875	$721.30	$721.30	$721.30