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	$105.88	5.291%	$111.4821	$111.48	$111.50	$111.50
Purchase #2	$233.47	11.745%	$260.8911	$260.89	$260.90	$260.90
Purchase #3	$236.73	13.630%	$268.9963	$269.00	$269.00	$269.00
Purchase #4	$99.74	5.598%	$105.3234	$105.32	$105.30	$105.30
Purchase #5	$45.25	9.598%	$49.5931	$49.59	$49.60	$49.60
Purchase #6	$216.93	11.607%	$242.1091	$242.11	$242.10	$242.10
Purchase #7	$54.26	12.833%	$61.2232	$61.22	$61.20	$61.20
7 purchase totals =	$992.26		$1,099.6183	$1,099.61	$1,099.60	$1,099.60