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	$190.89	6.574%	$203.4391	$203.44	$203.45	$203.40
Purchase #2	$237.63	4.317%	$247.8885	$247.89	$247.90	$247.90
Purchase #3	$70.57	6.438%	$75.1133	$75.11	$75.10	$75.10
Purchase #4	$149.72	3.113%	$154.3808	$154.38	$154.40	$154.40
Purchase #5	$247.82	5.676%	$261.8863	$261.89	$261.90	$261.90
Purchase #6	$82.51	9.825%	$90.6166	$90.62	$90.60	$90.60
Purchase #7	$154.56	5.444%	$162.9742	$162.97	$162.95	$163.00
7 purchase totals =	$1,133.70		$1,196.2988	$1,196.30	$1,196.30	$1,196.30