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	$248.60	6.200%	$264.0132	$264.01	$264.00	$264.00
Purchase #2	$108.94	13.759%	$123.9291	$123.93	$123.95	$123.90
Purchase #3	$190.64	4.843%	$199.8727	$199.87	$199.85	$199.90
Purchase #4	$86.70	5.432%	$91.4095	$91.41	$91.40	$91.40
Purchase #5	$64.78	11.769%	$72.404	$72.40	$72.40	$72.40
Purchase #6	$29.46	13.863%	$33.544	$33.54	$33.55	$33.50
Purchase #7	$193.63	3.460%	$200.3296	$200.33	$200.35	$200.30
7 purchase totals =	$922.75		$985.5021	$985.49	$985.50	$985.40