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	$31.60	4.274%	$32.9506	$32.95	$32.95	$33.00
Purchase #2	$39.85	13.170%	$45.0982	$45.10	$45.10	$45.10
Purchase #3	$81.55	7.307%	$87.5089	$87.51	$87.50	$87.50
Purchase #4	$180.49	4.459%	$188.538	$188.54	$188.55	$188.50
Purchase #5	$62.31	7.705%	$67.111	$67.11	$67.10	$67.10
Purchase #6	$10.83	13.759%	$12.3201	$12.32	$12.30	$12.30
Purchase #7	$140.87	10.205%	$155.2458	$155.25	$155.25	$155.20
7 purchase totals =	$547.50		$588.7726	$588.78	$588.75	$588.70