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	$92.78	7.766%	$99.9853	$99.99	$100.00	$100.00
Purchase #2	$126.58	12.418%	$142.2987	$142.30	$142.30	$142.30
Purchase #3	$186.83	7.532%	$200.902	$200.90	$200.90	$200.90
Purchase #4	$232.96	6.491%	$248.0814	$248.08	$248.10	$248.10
Purchase #5	$77.35	6.372%	$82.2787	$82.28	$82.30	$82.30
Purchase #6	$40.37	7.155%	$43.2585	$43.26	$43.25	$43.30
Purchase #7	$186.99	4.627%	$195.642	$195.64	$195.65	$195.60
7 purchase totals =	$943.86		$1,012.4466	$1,012.45	$1,012.50	$1,012.50