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	$54.31	10.723%	$60.1337	$60.13	$60.15	$60.10
Purchase #2	$89.46	7.467%	$96.14	$96.14	$96.15	$96.10
Purchase #3	$75.48	13.116%	$85.38	$85.38	$85.40	$85.40
Purchase #4	$81.44	10.822%	$90.2534	$90.25	$90.25	$90.30
Purchase #5	$204.67	12.139%	$229.5149	$229.51	$229.50	$229.50
Purchase #6	$18.96	7.504%	$20.3828	$20.38	$20.40	$20.40
Purchase #7	$141.93	3.746%	$147.2467	$147.25	$147.25	$147.20
7 purchase totals =	$666.25		$729.0515	$729.04	$729.10	$729.00