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	$162.47	13.829%	$184.938	$184.94	$184.95	$184.90
Purchase #2	$45.70	13.414%	$51.8302	$51.83	$51.85	$51.80
Purchase #3	$248.78	7.873%	$268.3664	$268.37	$268.35	$268.40
Purchase #4	$85.34	3.683%	$88.4831	$88.48	$88.50	$88.50
Purchase #5	$49.59	7.504%	$53.3112	$53.31	$53.30	$53.30
Purchase #6	$88.73	12.124%	$99.4876	$99.49	$99.50	$99.50
Purchase #7	$153.86	8.768%	$167.3504	$167.35	$167.35	$167.40
7 purchase totals =	$834.47		$913.7669	$913.77	$913.80	$913.80