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	$119.72	5.476%	$126.2759	$126.28	$126.30	$126.30
Purchase #2	$112.55	13.379%	$127.6081	$127.61	$127.60	$127.60
Purchase #3	$172.93	3.314%	$178.6609	$178.66	$178.65	$178.70
Purchase #4	$18.48	5.374%	$19.4731	$19.47	$19.45	$19.50
Purchase #5	$74.65	5.273%	$78.5863	$78.59	$78.60	$78.60
Purchase #6	$223.98	7.140%	$239.9722	$239.97	$239.95	$240.00
Purchase #7	$51.33	7.649%	$55.2562	$55.26	$55.25	$55.30
7 purchase totals =	$773.64		$825.8327	$825.84	$825.80	$826.00