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	$212.39	11.703%	$237.246	$237.25	$237.25	$237.20
Purchase #2	$48.78	3.295%	$50.3873	$50.39	$50.40	$50.40
Purchase #3	$29.54	8.601%	$32.0807	$32.08	$32.10	$32.10
Purchase #4	$209.32	9.792%	$229.8166	$229.82	$229.80	$229.80
Purchase #5	$42.61	5.696%	$45.0371	$45.04	$45.05	$45.00
Purchase #6	$41.95	8.182%	$45.3823	$45.38	$45.40	$45.40
Purchase #7	$142.90	13.718%	$162.503	$162.50	$162.50	$162.50
7 purchase totals =	$727.49		$802.4530	$802.46	$802.50	$802.40