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	$7.59	8.735%	$8.253	$8.25	$8.25	$8.30
Purchase #2	$204.85	8.738%	$222.7498	$222.75	$222.75	$222.70
Purchase #3	$80.96	11.517%	$90.2842	$90.28	$90.30	$90.30
Purchase #4	$153.59	3.789%	$159.4095	$159.41	$159.40	$159.40
Purchase #5	$21.94	13.133%	$24.8214	$24.82	$24.80	$24.80
Purchase #6	$90.79	13.411%	$102.9658	$102.97	$102.95	$103.00
Purchase #7	$175.84	4.708%	$184.1185	$184.12	$184.10	$184.10
7 purchase totals =	$735.56		$792.6022	$792.60	$792.55	$792.60