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	$165.66	12.794%	$186.8545	$186.85	$186.85	$186.90
Purchase #2	$165.60	11.576%	$184.7699	$184.77	$184.75	$184.80
Purchase #3	$15.80	9.276%	$17.2656	$17.27	$17.25	$17.30
Purchase #4	$233.71	9.208%	$255.23	$255.23	$255.25	$255.20
Purchase #5	$174.77	6.610%	$186.3223	$186.32	$186.30	$186.30
Purchase #6	$83.32	9.835%	$91.5145	$91.51	$91.50	$91.50
Purchase #7	$90.95	3.617%	$94.2397	$94.24	$94.25	$94.20
7 purchase totals =	$929.81		$1,016.1965	$1,016.19	$1,016.15	$1,016.20