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	$35.36	5.304%	$37.2355	$37.24	$37.25	$37.20
Purchase #2	$112.54	13.611%	$127.8578	$127.86	$127.85	$127.90
Purchase #3	$67.94	10.525%	$75.0907	$75.09	$75.10	$75.10
Purchase #4	$200.65	3.224%	$207.119	$207.12	$207.10	$207.10
Purchase #5	$48.89	4.627%	$51.1521	$51.15	$51.15	$51.20
Purchase #6	$47.56	10.712%	$52.6546	$52.65	$52.65	$52.70
Purchase #7	$189.61	10.781%	$210.0519	$210.05	$210.05	$210.10
7 purchase totals =	$702.55		$761.1616	$761.16	$761.15	$761.30