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	$198.27	3.425%	$205.0607	$205.06	$205.05	$205.10
Purchase #2	$25.74	13.199%	$29.1374	$29.14	$29.15	$29.10
Purchase #3	$88.66	12.261%	$99.5306	$99.53	$99.55	$99.50
Purchase #4	$113.57	5.202%	$119.4779	$119.48	$119.50	$119.50
Purchase #5	$78.32	9.437%	$85.7111	$85.71	$85.70	$85.70
Purchase #6	$41.98	4.815%	$44.0013	$44.00	$44.00	$44.00
Purchase #7	$57.26	4.203%	$59.6666	$59.67	$59.65	$59.70
7 purchase totals =	$603.80		$642.5856	$642.59	$642.60	$642.60