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	$244.84	11.771%	$273.6601	$273.66	$273.65	$273.70
Purchase #2	$229.73	5.379%	$242.0872	$242.09	$242.10	$242.10
Purchase #3	$140.73	7.150%	$150.7922	$150.79	$150.80	$150.80
Purchase #4	$85.28	12.321%	$95.7873	$95.79	$95.80	$95.80
Purchase #5	$158.88	13.235%	$179.9078	$179.91	$179.90	$179.90
Purchase #6	$55.86	10.799%	$61.8923	$61.89	$61.90	$61.90
Purchase #7	$136.49	8.703%	$148.3687	$148.37	$148.35	$148.40
7 purchase totals =	$1,051.81		$1,152.4956	$1,152.50	$1,152.50	$1,152.60