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	$196.90	12.350%	$221.2172	$221.22	$221.20	$221.20
Purchase #2	$239.52	13.273%	$271.3115	$271.31	$271.30	$271.30
Purchase #3	$81.48	13.133%	$92.1808	$92.18	$92.20	$92.20
Purchase #4	$210.33	9.845%	$231.037	$231.04	$231.05	$231.00
Purchase #5	$140.73	7.234%	$150.9104	$150.91	$150.90	$150.90
Purchase #6	$191.85	10.266%	$211.5453	$211.55	$211.55	$211.50
Purchase #7	$35.58	6.463%	$37.8795	$37.88	$37.90	$37.90
7 purchase totals =	$1,096.39		$1,216.0817	$1,216.09	$1,216.10	$1,216.00