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	$143.44	13.483%	$162.78	$162.78	$162.80	$162.80
Purchase #2	$123.49	11.533%	$137.7321	$137.73	$137.75	$137.70
Purchase #3	$213.40	7.132%	$228.6197	$228.62	$228.60	$228.60
Purchase #4	$100.97	4.369%	$105.3814	$105.38	$105.40	$105.40
Purchase #5	$197.55	6.357%	$210.1083	$210.11	$210.10	$210.10
Purchase #6	$96.73	8.583%	$105.0323	$105.03	$105.05	$105.00
Purchase #7	$79.32	7.808%	$85.5133	$85.51	$85.50	$85.50
7 purchase totals =	$954.90		$1,035.1671	$1,035.16	$1,035.20	$1,035.10