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	$50.89	13.485%	$57.7525	$57.75	$57.75	$57.80
Purchase #2	$11.55	13.607%	$13.1216	$13.12	$13.10	$13.10
Purchase #3	$19.35	4.450%	$20.2111	$20.21	$20.20	$20.20
Purchase #4	$54.72	13.121%	$61.8998	$61.90	$61.90	$61.90
Purchase #5	$154.30	5.459%	$162.7232	$162.72	$162.70	$162.70
Purchase #6	$234.53	11.241%	$260.8935	$260.89	$260.90	$260.90
Purchase #7	$28.33	12.845%	$31.969	$31.97	$31.95	$32.00
7 purchase totals =	$553.67		$608.5707	$608.56	$608.50	$608.60