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	$98.48	6.857%	$105.2328	$105.23	$105.25	$105.20
Purchase #2	$95.66	10.783%	$105.975	$105.98	$106.00	$106.00
Purchase #3	$74.63	10.201%	$82.243	$82.24	$82.25	$82.20
Purchase #4	$13.56	11.637%	$15.138	$15.14	$15.15	$15.10
Purchase #5	$134.69	3.461%	$139.3516	$139.35	$139.35	$139.40
Purchase #6	$146.91	13.801%	$167.185	$167.19	$167.20	$167.20
Purchase #7	$94.56	13.373%	$107.2055	$107.21	$107.20	$107.20
7 purchase totals =	$658.49		$722.3309	$722.34	$722.40	$722.30