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	$150.30	9.173%	$164.087	$164.09	$164.10	$164.10
Purchase #2	$201.79	6.355%	$214.6138	$214.61	$214.60	$214.60
Purchase #3	$32.53	9.632%	$35.6633	$35.66	$35.65	$35.70
Purchase #4	$237.96	10.494%	$262.9315	$262.93	$262.95	$262.90
Purchase #5	$52.50	10.262%	$57.8876	$57.89	$57.90	$57.90
Purchase #6	$245.31	7.435%	$263.5488	$263.55	$263.55	$263.50
Purchase #7	$127.91	3.640%	$132.5659	$132.57	$132.55	$132.60
7 purchase totals =	$1,048.30		$1,131.2979	$1,131.30	$1,131.30	$1,131.30