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	$87.41	5.215%	$91.9684	$91.97	$91.95	$92.00
Purchase #2	$20.80	9.805%	$22.8394	$22.84	$22.85	$22.80
Purchase #3	$205.81	3.745%	$213.5176	$213.52	$213.50	$213.50
Purchase #4	$85.42	6.164%	$90.6853	$90.69	$90.70	$90.70
Purchase #5	$109.81	7.337%	$117.8668	$117.87	$117.85	$117.90
Purchase #6	$82.30	8.736%	$89.4897	$89.49	$89.50	$89.50
Purchase #7	$247.62	10.365%	$273.2858	$273.29	$273.30	$273.30
7 purchase totals =	$839.17		$899.6530	$899.67	$899.65	$899.70