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	$190.33	4.316%	$198.5446	$198.54	$198.55	$198.50
Purchase #2	$233.50	3.746%	$242.2469	$242.25	$242.25	$242.20
Purchase #3	$133.89	4.454%	$139.8535	$139.85	$139.85	$139.90
Purchase #4	$181.49	13.192%	$205.4322	$205.43	$205.45	$205.40
Purchase #5	$78.44	8.598%	$85.1843	$85.18	$85.20	$85.20
Purchase #6	$31.96	8.293%	$34.6104	$34.61	$34.60	$34.60
Purchase #7	$195.33	11.650%	$218.0859	$218.09	$218.10	$218.10
7 purchase totals =	$1,044.94		$1,123.9578	$1,123.95	$1,124.00	$1,123.90