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	$165.94	6.270%	$176.3444	$176.34	$176.35	$176.30
Purchase #2	$111.91	7.816%	$120.6569	$120.66	$120.65	$120.70
Purchase #3	$37.27	9.775%	$40.9131	$40.91	$40.90	$40.90
Purchase #4	$26.61	7.492%	$28.6036	$28.60	$28.60	$28.60
Purchase #5	$62.56	10.216%	$68.9511	$68.95	$68.95	$69.00
Purchase #6	$78.27	8.722%	$85.0967	$85.10	$85.10	$85.10
Purchase #7	$81.77	6.232%	$86.8659	$86.87	$86.85	$86.90
7 purchase totals =	$564.33		$607.4317	$607.43	$607.40	$607.50