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	$53.80	9.346%	$58.8281	$58.83	$58.85	$58.80
Purchase #2	$116.52	12.611%	$131.2143	$131.21	$131.20	$131.20
Purchase #3	$91.48	3.826%	$94.98	$94.98	$95.00	$95.00
Purchase #4	$37.87	7.747%	$40.8038	$40.80	$40.80	$40.80
Purchase #5	$79.36	9.606%	$86.9833	$86.98	$87.00	$87.00
Purchase #6	$32.41	10.362%	$35.7683	$35.77	$35.75	$35.80
Purchase #7	$41.89	10.571%	$46.3182	$46.32	$46.30	$46.30
7 purchase totals =	$453.33		$494.8960	$494.89	$494.90	$494.90