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	$113.73	11.826%	$127.1797	$127.18	$127.20	$127.20
Purchase #2	$218.33	3.667%	$226.3362	$226.34	$226.35	$226.30
Purchase #3	$205.94	8.188%	$222.8024	$222.80	$222.80	$222.80
Purchase #4	$85.47	12.599%	$96.2384	$96.24	$96.25	$96.20
Purchase #5	$132.77	5.377%	$139.909	$139.91	$139.90	$139.90
Purchase #6	$191.27	3.602%	$198.1595	$198.16	$198.15	$198.20
Purchase #7	$13.33	4.113%	$13.8783	$13.88	$13.90	$13.90
7 purchase totals =	$960.84		$1,024.5035	$1,024.51	$1,024.55	$1,024.50