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	$17.76	7.594%	$19.1087	$19.11	$19.10	$19.10
Purchase #2	$144.78	12.375%	$162.6965	$162.70	$162.70	$162.70
Purchase #3	$53.72	10.570%	$59.3982	$59.40	$59.40	$59.40
Purchase #4	$13.93	6.586%	$14.8474	$14.85	$14.85	$14.80
Purchase #5	$78.68	11.487%	$87.718	$87.72	$87.70	$87.70
Purchase #6	$51.56	4.868%	$54.0699	$54.07	$54.05	$54.10
Purchase #7	$37.32	8.497%	$40.4911	$40.49	$40.50	$40.50
7 purchase totals =	$397.75		$438.3298	$438.34	$438.30	$438.30