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	$203.92	9.788%	$223.8797	$223.88	$223.90	$223.90
Purchase #2	$168.89	5.651%	$178.434	$178.43	$178.45	$178.40
Purchase #3	$118.34	8.104%	$127.9303	$127.93	$127.95	$127.90
Purchase #4	$164.28	9.305%	$179.5663	$179.57	$179.55	$179.60
Purchase #5	$180.35	5.119%	$189.5821	$189.58	$189.60	$189.60
Purchase #6	$176.82	6.626%	$188.5361	$188.54	$188.55	$188.50
Purchase #7	$18.38	3.374%	$19.0001	$19.00	$19.00	$19.00
7 purchase totals =	$1,030.98		$1,106.9286	$1,106.93	$1,107.00	$1,106.90