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	$213.93	11.421%	$238.3629	$238.36	$238.35	$238.40
Purchase #2	$107.56	3.630%	$111.4644	$111.46	$111.45	$111.50
Purchase #3	$64.42	10.835%	$71.3999	$71.40	$71.40	$71.40
Purchase #4	$151.68	3.166%	$156.4822	$156.48	$156.50	$156.50
Purchase #5	$133.52	12.699%	$150.4757	$150.48	$150.50	$150.50
Purchase #6	$248.75	10.395%	$274.6076	$274.61	$274.60	$274.60
Purchase #7	$249.97	10.395%	$275.9544	$275.95	$275.95	$276.00
7 purchase totals =	$1,169.83		$1,278.7471	$1,278.74	$1,278.75	$1,278.90