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	$59.85	8.366%	$64.8571	$64.86	$64.85	$64.90
Purchase #2	$244.88	8.233%	$265.041	$265.04	$265.05	$265.00
Purchase #3	$91.90	7.688%	$98.9653	$98.97	$98.95	$99.00
Purchase #4	$73.51	11.510%	$81.971	$81.97	$81.95	$82.00
Purchase #5	$88.41	13.696%	$100.5186	$100.52	$100.50	$100.50
Purchase #6	$241.71	11.109%	$268.5616	$268.56	$268.55	$268.60
Purchase #7	$47.62	5.827%	$50.3948	$50.39	$50.40	$50.40
7 purchase totals =	$847.88		$930.3094	$930.31	$930.25	$930.40