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	$158.90	8.150%	$171.8504	$171.85	$171.85	$171.90
Purchase #2	$83.93	3.509%	$86.8751	$86.88	$86.90	$86.90
Purchase #3	$178.92	4.731%	$187.3847	$187.38	$187.40	$187.40
Purchase #4	$248.70	11.675%	$277.7357	$277.74	$277.75	$277.70
Purchase #5	$31.45	11.857%	$35.179	$35.18	$35.20	$35.20
Purchase #6	$62.38	11.599%	$69.6155	$69.62	$69.60	$69.60
Purchase #7	$165.36	5.762%	$174.888	$174.89	$174.90	$174.90
7 purchase totals =	$929.64		$1,003.5284	$1,003.54	$1,003.60	$1,003.60