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	$53.48	6.451%	$56.93	$56.93	$56.95	$56.90
Purchase #2	$45.40	11.149%	$50.4616	$50.46	$50.45	$50.50
Purchase #3	$178.29	13.798%	$202.8905	$202.89	$202.90	$202.90
Purchase #4	$199.91	6.812%	$213.5279	$213.53	$213.55	$213.50
Purchase #5	$213.69	7.183%	$229.0394	$229.04	$229.05	$229.00
Purchase #6	$247.42	5.831%	$261.8471	$261.85	$261.85	$261.80
Purchase #7	$85.42	13.709%	$97.1302	$97.13	$97.15	$97.10
7 purchase totals =	$1,023.61		$1,111.8267	$1,111.83	$1,111.90	$1,111.70