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	$232.76	10.761%	$257.8073	$257.81	$257.80	$257.80
Purchase #2	$224.54	13.473%	$254.7923	$254.79	$254.80	$254.80
Purchase #3	$13.48	11.527%	$15.0338	$15.03	$15.05	$15.00
Purchase #4	$96.27	13.663%	$109.4234	$109.42	$109.40	$109.40
Purchase #5	$56.40	5.584%	$59.5494	$59.55	$59.55	$59.50
Purchase #6	$33.50	4.620%	$35.0477	$35.05	$35.05	$35.00
Purchase #7	$20.65	4.533%	$21.5861	$21.59	$21.60	$21.60
7 purchase totals =	$677.60		$753.2400	$753.24	$753.25	$753.10