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	$19.34	7.701%	$20.8294	$20.83	$20.85	$20.80
Purchase #2	$96.76	13.148%	$109.482	$109.48	$109.50	$109.50
Purchase #3	$11.45	7.145%	$12.2681	$12.27	$12.25	$12.30
Purchase #4	$39.62	12.643%	$44.6292	$44.63	$44.65	$44.60
Purchase #5	$80.91	6.414%	$86.0996	$86.10	$86.10	$86.10
Purchase #6	$37.90	11.442%	$42.2365	$42.24	$42.25	$42.20
Purchase #7	$131.49	11.256%	$146.2905	$146.29	$146.30	$146.30
7 purchase totals =	$417.47		$461.8353	$461.84	$461.90	$461.80