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	$91.44	4.460%	$95.5182	$95.52	$95.50	$95.50
Purchase #2	$9.51	3.161%	$9.8106	$9.81	$9.80	$9.80
Purchase #3	$234.60	11.315%	$261.145	$261.15	$261.15	$261.10
Purchase #4	$90.58	12.418%	$101.8282	$101.83	$101.85	$101.80
Purchase #5	$54.95	8.395%	$59.5631	$59.56	$59.55	$59.60
Purchase #6	$157.46	9.436%	$172.3179	$172.32	$172.30	$172.30
Purchase #7	$200.37	4.443%	$209.2724	$209.27	$209.25	$209.30
7 purchase totals =	$838.91		$909.4554	$909.46	$909.40	$909.40