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	$161.90	10.777%	$179.348	$179.35	$179.35	$179.30
Purchase #2	$82.82	8.390%	$89.7686	$89.77	$89.75	$89.80
Purchase #3	$69.38	4.529%	$72.5222	$72.52	$72.50	$72.50
Purchase #4	$33.73	4.843%	$35.3635	$35.36	$35.35	$35.40
Purchase #5	$37.38	6.235%	$39.7106	$39.71	$39.70	$39.70
Purchase #6	$95.66	6.327%	$101.7124	$101.71	$101.70	$101.70
Purchase #7	$51.45	12.687%	$57.9775	$57.98	$58.00	$58.00
7 purchase totals =	$532.32		$576.4028	$576.40	$576.35	$576.40