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	$33.98	4.772%	$35.6015	$35.60	$35.60	$35.60
Purchase #2	$183.35	13.820%	$208.689	$208.69	$208.70	$208.70
Purchase #3	$133.35	5.353%	$140.4882	$140.49	$140.50	$140.50
Purchase #4	$83.32	3.137%	$85.9337	$85.93	$85.95	$85.90
Purchase #5	$210.92	5.739%	$223.0247	$223.02	$223.00	$223.00
Purchase #6	$249.94	11.417%	$278.4756	$278.48	$278.50	$278.50
Purchase #7	$250.43	7.232%	$268.5411	$268.54	$268.55	$268.50
7 purchase totals =	$1,145.29		$1,240.7538	$1,240.75	$1,240.80	$1,240.70