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	$12.76	7.508%	$13.718	$13.72	$13.70	$13.70
Purchase #2	$59.66	4.327%	$62.2415	$62.24	$62.25	$62.20
Purchase #3	$97.33	5.209%	$102.3999	$102.40	$102.40	$102.40
Purchase #4	$86.94	3.408%	$89.9029	$89.90	$89.90	$89.90
Purchase #5	$78.75	12.291%	$88.4292	$88.43	$88.45	$88.40
Purchase #6	$244.96	8.529%	$265.8526	$265.85	$265.85	$265.90
Purchase #7	$86.33	11.219%	$96.0154	$96.02	$96.00	$96.00
7 purchase totals =	$666.73		$718.5595	$718.56	$718.55	$718.50