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	$60.77	4.604%	$63.5679	$63.57	$63.55	$63.60
Purchase #2	$46.81	7.700%	$50.4144	$50.41	$50.40	$50.40
Purchase #3	$144.55	11.231%	$160.7844	$160.78	$160.80	$160.80
Purchase #4	$197.87	12.528%	$222.6592	$222.66	$222.65	$222.70
Purchase #5	$247.98	3.182%	$255.8707	$255.87	$255.85	$255.90
Purchase #6	$153.50	5.710%	$162.2649	$162.26	$162.25	$162.30
Purchase #7	$160.56	12.214%	$180.1708	$180.17	$180.15	$180.20
7 purchase totals =	$1,012.04		$1,095.7323	$1,095.72	$1,095.65	$1,095.90