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	$165.76	11.502%	$184.8257	$184.83	$184.85	$184.80
Purchase #2	$182.86	3.382%	$189.0443	$189.04	$189.05	$189.00
Purchase #3	$54.78	12.258%	$61.4949	$61.49	$61.50	$61.50
Purchase #4	$221.96	6.112%	$235.5262	$235.53	$235.55	$235.50
Purchase #5	$171.45	10.742%	$189.8672	$189.87	$189.85	$189.90
Purchase #6	$160.79	4.780%	$168.4758	$168.48	$168.50	$168.50
Purchase #7	$180.28	5.273%	$189.7862	$189.79	$189.80	$189.80
7 purchase totals =	$1,137.88		$1,219.0203	$1,219.03	$1,219.10	$1,219.00