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	$81.54	11.396%	$90.8323	$90.83	$90.85	$90.80
Purchase #2	$11.30	6.264%	$12.0078	$12.01	$12.00	$12.00
Purchase #3	$239.41	9.281%	$261.6296	$261.63	$261.65	$261.60
Purchase #4	$20.25	5.623%	$21.3887	$21.39	$21.40	$21.40
Purchase #5	$217.46	11.214%	$241.846	$241.85	$241.85	$241.80
Purchase #6	$29.62	12.814%	$33.4155	$33.42	$33.40	$33.40
Purchase #7	$193.40	10.314%	$213.3473	$213.35	$213.35	$213.30
7 purchase totals =	$792.98		$874.4672	$874.48	$874.50	$874.30