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	$209.36	11.713%	$233.8823	$233.88	$233.90	$233.90
Purchase #2	$203.60	5.280%	$214.3501	$214.35	$214.35	$214.40
Purchase #3	$78.60	10.181%	$86.6023	$86.60	$86.60	$86.60
Purchase #4	$141.88	6.186%	$150.6567	$150.66	$150.65	$150.70
Purchase #5	$39.45	10.220%	$43.4818	$43.48	$43.50	$43.50
Purchase #6	$128.54	4.221%	$133.9657	$133.97	$133.95	$134.00
Purchase #7	$143.71	4.408%	$150.0447	$150.04	$150.05	$150.00
7 purchase totals =	$945.14		$1,012.9836	$1,012.98	$1,013.00	$1,013.10