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	$87.51	5.402%	$92.2373	$92.24	$92.25	$92.20
Purchase #2	$174.70	8.602%	$189.7277	$189.73	$189.75	$189.70
Purchase #3	$186.87	9.482%	$204.589	$204.59	$204.60	$204.60
Purchase #4	$80.59	10.635%	$89.1607	$89.16	$89.15	$89.20
Purchase #5	$115.65	11.191%	$128.5924	$128.59	$128.60	$128.60
Purchase #6	$109.72	7.267%	$117.6934	$117.69	$117.70	$117.70
Purchase #7	$212.35	6.171%	$225.4541	$225.45	$225.45	$225.50
7 purchase totals =	$967.39		$1,047.4546	$1,047.45	$1,047.50	$1,047.50