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	$104.31	11.454%	$116.2577	$116.26	$116.25	$116.30
Purchase #2	$156.71	13.743%	$178.2467	$178.25	$178.25	$178.20
Purchase #3	$150.28	7.232%	$161.1482	$161.15	$161.15	$161.10
Purchase #4	$182.91	12.253%	$205.322	$205.32	$205.30	$205.30
Purchase #5	$80.55	10.831%	$89.2744	$89.27	$89.25	$89.30
Purchase #6	$163.34	5.505%	$172.3319	$172.33	$172.35	$172.30
Purchase #7	$94.41	10.493%	$104.3164	$104.32	$104.30	$104.30
7 purchase totals =	$932.51		$1,026.8973	$1,026.90	$1,026.85	$1,026.80