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	$171.25	11.728%	$191.3342	$191.33	$191.35	$191.30
Purchase #2	$235.70	10.115%	$259.5411	$259.54	$259.55	$259.50
Purchase #3	$13.36	8.218%	$14.4579	$14.46	$14.45	$14.50
Purchase #4	$140.50	13.816%	$159.9115	$159.91	$159.90	$159.90
Purchase #5	$132.98	6.553%	$141.6942	$141.69	$141.70	$141.70
Purchase #6	$94.90	3.399%	$98.1257	$98.13	$98.15	$98.10
Purchase #7	$200.38	8.740%	$217.8932	$217.89	$217.90	$217.90
7 purchase totals =	$989.07		$1,082.9578	$1,082.95	$1,083.00	$1,082.90