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	$83.73	7.596%	$90.0901	$90.09	$90.10	$90.10
Purchase #2	$156.93	9.674%	$172.1114	$172.11	$172.10	$172.10
Purchase #3	$62.88	13.859%	$71.5945	$71.59	$71.60	$71.60
Purchase #4	$152.62	9.752%	$167.5035	$167.50	$167.50	$167.50
Purchase #5	$6.84	8.658%	$7.4322	$7.43	$7.45	$7.40
Purchase #6	$45.66	13.641%	$51.8885	$51.89	$51.90	$51.90
Purchase #7	$223.40	13.523%	$253.6104	$253.61	$253.60	$253.60
7 purchase totals =	$732.06		$814.2306	$814.22	$814.25	$814.20