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	$111.32	9.464%	$121.8553	$121.86	$121.85	$121.90
Purchase #2	$57.37	4.564%	$59.9884	$59.99	$60.00	$60.00
Purchase #3	$88.70	13.250%	$100.4528	$100.45	$100.45	$100.50
Purchase #4	$213.43	4.144%	$222.2745	$222.27	$222.25	$222.30
Purchase #5	$54.88	11.234%	$61.0452	$61.05	$61.05	$61.00
Purchase #6	$104.39	9.549%	$114.3582	$114.36	$114.35	$114.40
Purchase #7	$194.25	6.533%	$206.9404	$206.94	$206.95	$206.90
7 purchase totals =	$824.34		$886.9148	$886.92	$886.90	$887.00