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	$22.47	8.481%	$24.3757	$24.38	$24.40	$24.40
Purchase #2	$135.92	6.789%	$145.1476	$145.15	$145.15	$145.10
Purchase #3	$43.59	7.410%	$46.82	$46.82	$46.80	$46.80
Purchase #4	$230.39	6.150%	$244.559	$244.56	$244.55	$244.60
Purchase #5	$206.63	3.746%	$214.3704	$214.37	$214.35	$214.40
Purchase #6	$210.58	5.693%	$222.5683	$222.57	$222.55	$222.60
Purchase #7	$222.67	11.581%	$248.4574	$248.46	$248.45	$248.50
7 purchase totals =	$1,072.25		$1,146.2984	$1,146.31	$1,146.25	$1,146.40