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	$105.51	5.591%	$111.4091	$111.41	$111.40	$111.40
Purchase #2	$192.58	10.320%	$212.4543	$212.45	$212.45	$212.50
Purchase #3	$70.40	4.442%	$73.5272	$73.53	$73.55	$73.50
Purchase #4	$175.95	7.811%	$189.6935	$189.69	$189.70	$189.70
Purchase #5	$158.69	6.207%	$168.5399	$168.54	$168.55	$168.50
Purchase #6	$18.93	12.691%	$21.3324	$21.33	$21.35	$21.30
Purchase #7	$27.67	6.497%	$29.4677	$29.47	$29.45	$29.50
7 purchase totals =	$749.73		$806.4241	$806.42	$806.45	$806.40