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	$79.66	5.154%	$83.7657	$83.77	$83.75	$83.80
Purchase #2	$85.89	7.344%	$92.1978	$92.20	$92.20	$92.20
Purchase #3	$56.48	9.472%	$61.8298	$61.83	$61.85	$61.80
Purchase #4	$167.71	7.602%	$180.4593	$180.46	$180.45	$180.50
Purchase #5	$243.38	11.380%	$271.0766	$271.08	$271.10	$271.10
Purchase #6	$95.27	4.677%	$99.7258	$99.73	$99.75	$99.70
Purchase #7	$125.47	12.829%	$141.5665	$141.57	$141.55	$141.60
7 purchase totals =	$853.86		$930.6215	$930.64	$930.65	$930.70