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	$21.29	7.345%	$22.8538	$22.85	$22.85	$22.90
Purchase #2	$33.69	12.317%	$37.8396	$37.84	$37.85	$37.80
Purchase #3	$93.60	7.259%	$100.3944	$100.39	$100.40	$100.40
Purchase #4	$222.89	10.325%	$245.9034	$245.90	$245.90	$245.90
Purchase #5	$141.98	9.255%	$155.1202	$155.12	$155.10	$155.10
Purchase #6	$33.59	6.819%	$35.8805	$35.88	$35.90	$35.90
Purchase #7	$167.87	10.509%	$185.5115	$185.51	$185.50	$185.50
7 purchase totals =	$714.91		$783.5034	$783.49	$783.50	$783.50