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	$187.64	6.650%	$200.1181	$200.12	$200.10	$200.10
Purchase #2	$89.84	11.253%	$99.9497	$99.95	$99.95	$99.90
Purchase #3	$15.69	5.837%	$16.6058	$16.61	$16.60	$16.60
Purchase #4	$144.94	3.270%	$149.6795	$149.68	$149.70	$149.70
Purchase #5	$104.96	4.185%	$109.3526	$109.35	$109.35	$109.40
Purchase #6	$152.75	7.693%	$164.5011	$164.50	$164.50	$164.50
Purchase #7	$171.35	4.553%	$179.1516	$179.15	$179.15	$179.20
7 purchase totals =	$867.17		$919.3584	$919.36	$919.35	$919.40