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	$100.59	5.514%	$106.1365	$106.14	$106.15	$106.10
Purchase #2	$97.30	9.199%	$106.2506	$106.25	$106.25	$106.30
Purchase #3	$179.29	11.843%	$200.5233	$200.52	$200.50	$200.50
Purchase #4	$137.92	3.443%	$142.6686	$142.67	$142.65	$142.70
Purchase #5	$37.90	12.127%	$42.4961	$42.50	$42.50	$42.50
Purchase #6	$32.40	4.801%	$33.9555	$33.96	$33.95	$34.00
Purchase #7	$223.87	11.388%	$249.3643	$249.36	$249.35	$249.40
7 purchase totals =	$809.27		$881.3949	$881.40	$881.35	$881.50