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	$233.57	13.648%	$265.4476	$265.45	$265.45	$265.40
Purchase #2	$202.69	13.516%	$230.0856	$230.09	$230.10	$230.10
Purchase #3	$108.77	10.710%	$120.4193	$120.42	$120.40	$120.40
Purchase #4	$170.37	9.712%	$186.9163	$186.92	$186.90	$186.90
Purchase #5	$88.98	12.514%	$100.115	$100.12	$100.10	$100.10
Purchase #6	$162.67	12.482%	$182.9745	$182.97	$182.95	$183.00
Purchase #7	$83.85	6.446%	$89.255	$89.26	$89.25	$89.30
7 purchase totals =	$1,050.90		$1,175.2133	$1,175.23	$1,175.15	$1,175.20