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	$201.42	12.772%	$227.1454	$227.15	$227.15	$227.10
Purchase #2	$201.36	13.808%	$229.1638	$229.16	$229.15	$229.20
Purchase #3	$90.63	4.866%	$95.0401	$95.04	$95.05	$95.00
Purchase #4	$71.79	9.704%	$78.7565	$78.76	$78.75	$78.80
Purchase #5	$85.65	4.667%	$89.6473	$89.65	$89.65	$89.60
Purchase #6	$122.90	5.408%	$129.5464	$129.55	$129.55	$129.50
Purchase #7	$146.57	3.402%	$151.5563	$151.56	$151.55	$151.60
7 purchase totals =	$920.32		$1,000.8558	$1,000.87	$1,000.85	$1,000.80