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	$218.79	9.216%	$238.9537	$238.95	$238.95	$239.00
Purchase #2	$157.64	13.232%	$178.4989	$178.50	$178.50	$178.50
Purchase #3	$90.63	9.696%	$99.4175	$99.42	$99.40	$99.40
Purchase #4	$172.33	4.224%	$179.6092	$179.61	$179.60	$179.60
Purchase #5	$33.26	5.630%	$35.1325	$35.13	$35.15	$35.10
Purchase #6	$24.91	10.649%	$27.5627	$27.56	$27.55	$27.60
Purchase #7	$56.51	4.563%	$59.0886	$59.09	$59.10	$59.10
7 purchase totals =	$754.07		$818.2631	$818.26	$818.25	$818.30