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	$73.36	13.634%	$83.3619	$83.36	$83.35	$83.40
Purchase #2	$221.38	12.751%	$249.6082	$249.61	$249.60	$249.60
Purchase #3	$73.74	6.592%	$78.6009	$78.60	$78.60	$78.60
Purchase #4	$159.53	3.649%	$165.3512	$165.35	$165.35	$165.40
Purchase #5	$112.32	11.379%	$125.1009	$125.10	$125.10	$125.10
Purchase #6	$69.72	5.437%	$73.5107	$73.51	$73.50	$73.50
Purchase #7	$82.87	8.718%	$90.0946	$90.09	$90.10	$90.10
7 purchase totals =	$792.92		$865.6284	$865.62	$865.60	$865.70