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	$71.89	8.738%	$78.1717	$78.17	$78.15	$78.20
Purchase #2	$146.64	12.363%	$164.7691	$164.77	$164.75	$164.80
Purchase #3	$215.47	3.180%	$222.3219	$222.32	$222.30	$222.30
Purchase #4	$166.45	8.403%	$180.4368	$180.44	$180.45	$180.40
Purchase #5	$130.48	6.619%	$139.1165	$139.12	$139.10	$139.10
Purchase #6	$176.99	8.806%	$192.5757	$192.58	$192.60	$192.60
Purchase #7	$114.59	9.176%	$125.1048	$125.10	$125.10	$125.10
7 purchase totals =	$1,022.51		$1,102.4965	$1,102.50	$1,102.45	$1,102.50