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	$183.76	8.631%	$199.6203	$199.62	$199.60	$199.60
Purchase #2	$38.66	8.322%	$41.8773	$41.88	$41.90	$41.90
Purchase #3	$223.90	11.380%	$249.3798	$249.38	$249.40	$249.40
Purchase #4	$67.67	7.159%	$72.5145	$72.51	$72.50	$72.50
Purchase #5	$20.59	8.195%	$22.2774	$22.28	$22.30	$22.30
Purchase #6	$165.62	13.844%	$188.5484	$188.55	$188.55	$188.50
Purchase #7	$198.80	11.658%	$221.9761	$221.98	$222.00	$222.00
7 purchase totals =	$899.00		$996.1938	$996.20	$996.25	$996.20