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	$150.92	13.852%	$171.8254	$171.83	$171.85	$171.80
Purchase #2	$217.90	13.780%	$247.9266	$247.93	$247.95	$247.90
Purchase #3	$208.25	11.333%	$231.851	$231.85	$231.85	$231.90
Purchase #4	$93.98	3.291%	$97.0729	$97.07	$97.05	$97.10
Purchase #5	$69.25	13.759%	$78.7781	$78.78	$78.80	$78.80
Purchase #6	$101.35	12.259%	$113.7745	$113.77	$113.75	$113.80
Purchase #7	$149.37	12.155%	$167.5259	$167.53	$167.55	$167.50
7 purchase totals =	$991.02		$1,108.7544	$1,108.76	$1,108.80	$1,108.80