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	$218.50	7.539%	$234.9727	$234.97	$234.95	$235.00
Purchase #2	$177.89	9.847%	$195.4068	$195.41	$195.40	$195.40
Purchase #3	$65.71	10.654%	$72.7107	$72.71	$72.70	$72.70
Purchase #4	$166.78	3.585%	$172.7591	$172.76	$172.75	$172.80
Purchase #5	$39.86	10.689%	$44.1206	$44.12	$44.10	$44.10
Purchase #6	$43.68	7.407%	$46.9154	$46.92	$46.90	$46.90
Purchase #7	$180.89	5.292%	$190.4627	$190.46	$190.45	$190.50
7 purchase totals =	$893.31		$957.3480	$957.35	$957.25	$957.40