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	$177.95	5.318%	$187.4134	$187.41	$187.40	$187.40
Purchase #2	$37.52	13.225%	$42.482	$42.48	$42.50	$42.50
Purchase #3	$136.26	5.394%	$143.6099	$143.61	$143.60	$143.60
Purchase #4	$52.63	12.304%	$59.1056	$59.11	$59.10	$59.10
Purchase #5	$96.90	7.303%	$103.9766	$103.98	$104.00	$104.00
Purchase #6	$147.63	6.564%	$157.3204	$157.32	$157.30	$157.30
Purchase #7	$47.67	10.814%	$52.825	$52.83	$52.85	$52.80
7 purchase totals =	$696.56		$746.7329	$746.74	$746.75	$746.70