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	$174.72	4.624%	$182.7991	$182.80	$182.80	$182.80
Purchase #2	$100.64	3.677%	$104.3405	$104.34	$104.35	$104.30
Purchase #3	$34.65	12.564%	$39.0034	$39.00	$39.00	$39.00
Purchase #4	$242.52	3.654%	$251.3817	$251.38	$251.40	$251.40
Purchase #5	$54.96	7.564%	$59.1172	$59.12	$59.10	$59.10
Purchase #6	$6.84	11.131%	$7.6014	$7.60	$7.60	$7.60
Purchase #7	$221.39	5.554%	$233.686	$233.69	$233.70	$233.70
7 purchase totals =	$835.72		$877.9293	$877.93	$877.95	$877.90