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	$209.81	13.438%	$238.0043	$238.00	$238.00	$238.00
Purchase #2	$33.57	12.808%	$37.8696	$37.87	$37.85	$37.90
Purchase #3	$99.63	5.148%	$104.759	$104.76	$104.75	$104.80
Purchase #4	$98.77	4.676%	$103.3885	$103.39	$103.40	$103.40
Purchase #5	$60.34	4.442%	$63.0203	$63.02	$63.00	$63.00
Purchase #6	$99.77	5.614%	$105.3711	$105.37	$105.35	$105.40
Purchase #7	$233.83	11.831%	$261.4944	$261.49	$261.50	$261.50
7 purchase totals =	$835.72		$913.9072	$913.90	$913.85	$914.00