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	$192.92	11.822%	$215.727	$215.73	$215.75	$215.70
Purchase #2	$109.76	13.224%	$124.2747	$124.27	$124.25	$124.30
Purchase #3	$19.95	3.170%	$20.5824	$20.58	$20.60	$20.60
Purchase #4	$250.89	6.215%	$266.4828	$266.48	$266.50	$266.50
Purchase #5	$28.46	11.828%	$31.8262	$31.83	$31.85	$31.80
Purchase #6	$248.68	4.270%	$259.2986	$259.30	$259.30	$259.30
Purchase #7	$229.83	8.847%	$250.1631	$250.16	$250.15	$250.20
7 purchase totals =	$1,080.49		$1,168.3548	$1,168.35	$1,168.40	$1,168.40