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	$32.39	10.576%	$35.8156	$35.82	$35.80	$35.80
Purchase #2	$95.79	9.506%	$104.8958	$104.90	$104.90	$104.90
Purchase #3	$111.43	10.373%	$122.9886	$122.99	$123.00	$123.00
Purchase #4	$28.86	7.295%	$30.9653	$30.97	$30.95	$31.00
Purchase #5	$78.49	13.536%	$89.1144	$89.11	$89.10	$89.10
Purchase #6	$63.83	6.114%	$67.7326	$67.73	$67.75	$67.70
Purchase #7	$237.36	7.448%	$255.0386	$255.04	$255.05	$255.00
7 purchase totals =	$648.15		$706.5509	$706.56	$706.55	$706.50