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	$171.55	9.267%	$187.4475	$187.45	$187.45	$187.40
Purchase #2	$35.31	6.155%	$37.4833	$37.48	$37.50	$37.50
Purchase #3	$165.81	7.220%	$177.7815	$177.78	$177.80	$177.80
Purchase #4	$44.69	10.749%	$49.4937	$49.49	$49.50	$49.50
Purchase #5	$13.31	11.160%	$14.7954	$14.80	$14.80	$14.80
Purchase #6	$109.78	12.423%	$123.418	$123.42	$123.40	$123.40
Purchase #7	$156.87	7.125%	$168.047	$168.05	$168.05	$168.00
7 purchase totals =	$697.32		$758.4664	$758.47	$758.50	$758.40