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	$173.67	9.534%	$190.2277	$190.23	$190.25	$190.20
Purchase #2	$166.63	13.509%	$189.14	$189.14	$189.15	$189.10
Purchase #3	$177.30	6.409%	$188.6632	$188.66	$188.65	$188.70
Purchase #4	$229.34	3.450%	$237.2522	$237.25	$237.25	$237.30
Purchase #5	$188.92	10.680%	$209.0967	$209.10	$209.10	$209.10
Purchase #6	$46.28	6.609%	$49.3386	$49.34	$49.35	$49.30
Purchase #7	$54.46	9.279%	$59.5133	$59.51	$59.50	$59.50
7 purchase totals =	$1,036.60		$1,123.2317	$1,123.23	$1,123.25	$1,123.20