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	$82.26	5.715%	$86.9612	$86.96	$86.95	$87.00
Purchase #2	$25.73	11.787%	$28.7628	$28.76	$28.75	$28.80
Purchase #3	$174.49	13.541%	$198.1177	$198.12	$198.10	$198.10
Purchase #4	$18.68	7.642%	$20.1075	$20.11	$20.10	$20.10
Purchase #5	$95.39	9.561%	$104.5102	$104.51	$104.50	$104.50
Purchase #6	$103.50	8.791%	$112.5987	$112.60	$112.60	$112.60
Purchase #7	$160.71	7.215%	$172.3052	$172.31	$172.30	$172.30
7 purchase totals =	$660.76		$723.3633	$723.37	$723.30	$723.40