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	$189.99	3.108%	$195.8949	$195.89	$195.90	$195.90
Purchase #2	$170.58	6.459%	$181.5978	$181.60	$181.60	$181.60
Purchase #3	$99.87	11.383%	$111.2382	$111.24	$111.25	$111.20
Purchase #4	$128.43	8.623%	$139.5045	$139.50	$139.50	$139.50
Purchase #5	$181.58	10.505%	$200.655	$200.66	$200.65	$200.70
Purchase #6	$148.56	10.658%	$164.3935	$164.39	$164.40	$164.40
Purchase #7	$112.63	11.139%	$125.1759	$125.18	$125.20	$125.20
7 purchase totals =	$1,031.64		$1,118.4598	$1,118.46	$1,118.50	$1,118.50