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	$225.69	12.595%	$254.1157	$254.12	$254.10	$254.10
Purchase #2	$132.75	5.723%	$140.3473	$140.35	$140.35	$140.30
Purchase #3	$92.96	4.234%	$96.8959	$96.90	$96.90	$96.90
Purchase #4	$175.30	9.695%	$192.2953	$192.30	$192.30	$192.30
Purchase #5	$194.55	11.303%	$216.54	$216.54	$216.55	$216.50
Purchase #6	$132.48	3.284%	$136.8306	$136.83	$136.85	$136.80
Purchase #7	$151.62	13.774%	$172.5041	$172.50	$172.50	$172.50
7 purchase totals =	$1,105.35		$1,209.5289	$1,209.54	$1,209.55	$1,209.40