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	$59.29	8.562%	$64.3664	$64.37	$64.35	$64.40
Purchase #2	$143.68	13.204%	$162.6515	$162.65	$162.65	$162.70
Purchase #3	$11.36	6.363%	$12.0828	$12.08	$12.10	$12.10
Purchase #4	$51.61	7.179%	$55.3151	$55.32	$55.30	$55.30
Purchase #5	$6.92	7.609%	$7.4465	$7.45	$7.45	$7.40
Purchase #6	$12.59	8.419%	$13.65	$13.65	$13.65	$13.70
Purchase #7	$111.28	6.828%	$118.8782	$118.88	$118.90	$118.90
7 purchase totals =	$396.73		$434.3905	$434.40	$434.40	$434.50