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	$80.59	7.310%	$86.4811	$86.48	$86.50	$86.50
Purchase #2	$91.55	3.746%	$94.9795	$94.98	$95.00	$95.00
Purchase #3	$23.50	12.390%	$26.4117	$26.41	$26.40	$26.40
Purchase #4	$118.94	10.270%	$131.1551	$131.16	$131.15	$131.20
Purchase #5	$125.52	9.805%	$137.8272	$137.83	$137.85	$137.80
Purchase #6	$82.73	9.842%	$90.8723	$90.87	$90.85	$90.90
Purchase #7	$33.59	5.712%	$35.5087	$35.51	$35.50	$35.50
7 purchase totals =	$556.42		$603.2356	$603.24	$603.25	$603.30