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	$49.72	5.321%	$52.3656	$52.37	$52.35	$52.40
Purchase #2	$105.85	3.819%	$109.8924	$109.89	$109.90	$109.90
Purchase #3	$242.36	11.712%	$270.7452	$270.75	$270.75	$270.70
Purchase #4	$62.26	6.237%	$66.1432	$66.14	$66.15	$66.10
Purchase #5	$89.78	4.696%	$93.9961	$94.00	$94.00	$94.00
Purchase #6	$238.64	3.722%	$247.5222	$247.52	$247.50	$247.50
Purchase #7	$180.89	5.467%	$190.7793	$190.78	$190.80	$190.80
7 purchase totals =	$969.50		$1,031.4440	$1,031.45	$1,031.45	$1,031.40