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	$58.64	6.565%	$62.4897	$62.49	$62.50	$62.50
Purchase #2	$81.28	4.700%	$85.1002	$85.10	$85.10	$85.10
Purchase #3	$171.36	9.204%	$187.132	$187.13	$187.15	$187.10
Purchase #4	$140.95	7.348%	$151.307	$151.31	$151.30	$151.30
Purchase #5	$216.31	6.699%	$230.8006	$230.80	$230.80	$230.80
Purchase #6	$134.60	4.840%	$141.1146	$141.11	$141.10	$141.10
Purchase #7	$233.70	8.683%	$253.9922	$253.99	$254.00	$254.00
7 purchase totals =	$1,036.84		$1,111.9363	$1,111.93	$1,111.95	$1,111.90