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	$218.98	9.749%	$240.3284	$240.33	$240.35	$240.30
Purchase #2	$36.92	11.747%	$41.257	$41.26	$41.25	$41.30
Purchase #3	$105.94	7.139%	$113.5031	$113.50	$113.50	$113.50
Purchase #4	$206.77	12.147%	$231.8864	$231.89	$231.90	$231.90
Purchase #5	$94.82	5.277%	$99.8237	$99.82	$99.80	$99.80
Purchase #6	$159.60	13.607%	$181.3168	$181.32	$181.30	$181.30
Purchase #7	$54.83	7.687%	$59.0448	$59.04	$59.05	$59.00
7 purchase totals =	$877.86		$967.1602	$967.16	$967.15	$967.10