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	$78.74	5.325%	$82.9329	$82.93	$82.95	$82.90
Purchase #2	$30.73	5.755%	$32.4985	$32.50	$32.50	$32.50
Purchase #3	$175.61	3.408%	$181.5948	$181.59	$181.60	$181.60
Purchase #4	$241.89	10.227%	$266.6281	$266.63	$266.65	$266.60
Purchase #5	$155.28	5.175%	$163.3157	$163.32	$163.30	$163.30
Purchase #6	$100.72	13.300%	$114.1158	$114.12	$114.10	$114.10
Purchase #7	$27.76	12.235%	$31.1564	$31.16	$31.15	$31.20
7 purchase totals =	$810.73		$872.2422	$872.25	$872.25	$872.20