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	$144.97	12.344%	$162.8651	$162.87	$162.85	$162.90
Purchase #2	$125.81	13.386%	$142.6509	$142.65	$142.65	$142.70
Purchase #3	$109.74	12.188%	$123.1151	$123.12	$123.10	$123.10
Purchase #4	$130.62	11.255%	$145.3213	$145.32	$145.30	$145.30
Purchase #5	$94.64	4.608%	$99.001	$99.00	$99.00	$99.00
Purchase #6	$51.72	8.705%	$56.2222	$56.22	$56.20	$56.20
Purchase #7	$157.33	3.651%	$163.0741	$163.07	$163.05	$163.10
7 purchase totals =	$814.83		$892.2497	$892.25	$892.15	$892.30