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	$128.32	13.452%	$145.5816	$145.58	$145.60	$145.60
Purchase #2	$183.36	3.736%	$190.2103	$190.21	$190.20	$190.20
Purchase #3	$211.89	10.645%	$234.4457	$234.45	$234.45	$234.40
Purchase #4	$183.42	3.764%	$190.3239	$190.32	$190.30	$190.30
Purchase #5	$109.77	12.524%	$123.5176	$123.52	$123.50	$123.50
Purchase #6	$9.98	9.256%	$10.9037	$10.90	$10.90	$10.90
Purchase #7	$93.60	13.142%	$105.9009	$105.90	$105.90	$105.90
7 purchase totals =	$920.34		$1,000.8837	$1,000.88	$1,000.85	$1,000.80