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	$171.65	6.484%	$182.7798	$182.78	$182.80	$182.80
Purchase #2	$70.53	5.603%	$74.4818	$74.48	$74.50	$74.50
Purchase #3	$34.48	7.788%	$37.1653	$37.17	$37.15	$37.20
Purchase #4	$54.26	10.371%	$59.8873	$59.89	$59.90	$59.90
Purchase #5	$56.63	5.279%	$59.6195	$59.62	$59.60	$59.60
Purchase #6	$74.41	3.721%	$77.1788	$77.18	$77.20	$77.20
Purchase #7	$96.72	13.156%	$109.4445	$109.44	$109.45	$109.40
7 purchase totals =	$558.68		$600.5570	$600.56	$600.60	$600.60