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	$86.75	3.648%	$89.9146	$89.91	$89.90	$89.90
Purchase #2	$161.81	9.776%	$177.6285	$177.63	$177.65	$177.60
Purchase #3	$104.40	6.454%	$111.138	$111.14	$111.15	$111.10
Purchase #4	$127.38	10.469%	$140.7154	$140.72	$140.70	$140.70
Purchase #5	$17.63	7.382%	$18.9314	$18.93	$18.95	$18.90
Purchase #6	$165.43	11.822%	$184.9871	$184.99	$185.00	$185.00
Purchase #7	$35.70	10.334%	$39.3892	$39.39	$39.40	$39.40
7 purchase totals =	$699.10		$762.7042	$762.71	$762.75	$762.60