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	$79.59	3.772%	$82.5921	$82.59	$82.60	$82.60
Purchase #2	$55.59	13.359%	$63.0163	$63.02	$63.00	$63.00
Purchase #3	$24.52	4.450%	$25.6111	$25.61	$25.60	$25.60
Purchase #4	$117.62	8.179%	$127.2401	$127.24	$127.25	$127.20
Purchase #5	$195.57	13.274%	$221.53	$221.53	$221.55	$221.50
Purchase #6	$73.70	13.638%	$83.7512	$83.75	$83.75	$83.80
Purchase #7	$188.51	7.429%	$202.5144	$202.51	$202.50	$202.50
7 purchase totals =	$735.10		$806.2552	$806.25	$806.25	$806.20