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	$56.69	8.495%	$61.5058	$61.51	$61.50	$61.50
Purchase #2	$77.76	9.695%	$85.2988	$85.30	$85.30	$85.30
Purchase #3	$217.30	12.173%	$243.7519	$243.75	$243.75	$243.80
Purchase #4	$168.68	6.127%	$179.015	$179.02	$179.00	$179.00
Purchase #5	$95.95	6.745%	$102.4218	$102.42	$102.40	$102.40
Purchase #6	$56.84	4.197%	$59.2256	$59.23	$59.25	$59.20
Purchase #7	$195.83	7.141%	$209.8142	$209.81	$209.80	$209.80
7 purchase totals =	$869.05		$941.0331	$941.04	$941.00	$941.00