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	$133.98	9.572%	$146.8046	$146.80	$146.80	$146.80
Purchase #2	$133.78	12.746%	$150.8316	$150.83	$150.85	$150.80
Purchase #3	$7.53	11.245%	$8.3767	$8.38	$8.40	$8.40
Purchase #4	$52.25	13.135%	$59.113	$59.11	$59.10	$59.10
Purchase #5	$94.29	10.368%	$104.066	$104.07	$104.05	$104.10
Purchase #6	$217.32	11.614%	$242.5595	$242.56	$242.55	$242.60
Purchase #7	$150.67	11.180%	$167.5149	$167.51	$167.50	$167.50
7 purchase totals =	$789.82		$879.2663	$879.26	$879.25	$879.30