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	$102.38	6.368%	$108.8996	$108.90	$108.90	$108.90
Purchase #2	$241.67	5.557%	$255.0996	$255.10	$255.10	$255.10
Purchase #3	$83.74	7.859%	$90.3211	$90.32	$90.30	$90.30
Purchase #4	$134.50	13.718%	$152.9507	$152.95	$152.95	$153.00
Purchase #5	$132.32	9.102%	$144.3638	$144.36	$144.35	$144.40
Purchase #6	$183.89	13.712%	$209.105	$209.11	$209.10	$209.10
Purchase #7	$93.56	11.305%	$104.137	$104.14	$104.15	$104.10
7 purchase totals =	$972.06		$1,064.8768	$1,064.88	$1,064.85	$1,064.90