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	$224.42	10.611%	$248.2332	$248.23	$248.25	$248.20
Purchase #2	$78.26	12.307%	$87.8915	$87.89	$87.90	$87.90
Purchase #3	$88.77	6.862%	$94.8614	$94.86	$94.85	$94.90
Purchase #4	$197.57	3.117%	$203.7283	$203.73	$203.75	$203.70
Purchase #5	$165.42	4.150%	$172.2849	$172.28	$172.30	$172.30
Purchase #6	$19.32	9.539%	$21.1629	$21.16	$21.15	$21.20
Purchase #7	$72.58	7.592%	$78.0903	$78.09	$78.10	$78.10
7 purchase totals =	$846.34		$906.2525	$906.24	$906.30	$906.30