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	$9.83	10.192%	$10.8319	$10.83	$10.85	$10.80
Purchase #2	$164.29	7.124%	$175.994	$175.99	$176.00	$176.00
Purchase #3	$55.30	6.781%	$59.0499	$59.05	$59.05	$59.00
Purchase #4	$238.54	11.505%	$265.984	$265.98	$266.00	$266.00
Purchase #5	$220.83	7.838%	$238.1387	$238.14	$238.15	$238.10
Purchase #6	$44.44	3.213%	$45.8679	$45.87	$45.85	$45.90
Purchase #7	$196.89	4.789%	$206.3191	$206.32	$206.30	$206.30
7 purchase totals =	$930.12		$1,002.1855	$1,002.18	$1,002.20	$1,002.10