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	$147.72	11.762%	$165.0948	$165.09	$165.10	$165.10
Purchase #2	$96.92	6.661%	$103.3758	$103.38	$103.40	$103.40
Purchase #3	$59.90	5.260%	$63.0507	$63.05	$63.05	$63.10
Purchase #4	$158.84	13.250%	$179.8863	$179.89	$179.90	$179.90
Purchase #5	$34.86	7.561%	$37.4958	$37.50	$37.50	$37.50
Purchase #6	$5.93	7.287%	$6.3621	$6.36	$6.35	$6.40
Purchase #7	$135.43	12.366%	$152.1773	$152.18	$152.20	$152.20
7 purchase totals =	$639.60		$707.4428	$707.45	$707.50	$707.60