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	$125.27	13.800%	$142.5573	$142.56	$142.55	$142.60
Purchase #2	$248.89	13.298%	$281.9874	$281.99	$282.00	$282.00
Purchase #3	$92.55	7.207%	$99.2201	$99.22	$99.20	$99.20
Purchase #4	$57.43	5.258%	$60.4497	$60.45	$60.45	$60.40
Purchase #5	$189.88	4.710%	$198.8233	$198.82	$198.80	$198.80
Purchase #6	$68.49	4.149%	$71.3317	$71.33	$71.35	$71.30
Purchase #7	$24.82	11.327%	$27.6314	$27.63	$27.65	$27.60
7 purchase totals =	$807.33		$882.0009	$882.00	$882.00	$881.90