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	$216.98	5.256%	$228.3845	$228.38	$228.40	$228.40
Purchase #2	$37.48	13.489%	$42.5357	$42.54	$42.55	$42.50
Purchase #3	$156.83	6.244%	$166.6225	$166.62	$166.60	$166.60
Purchase #4	$90.40	7.620%	$97.2885	$97.29	$97.30	$97.30
Purchase #5	$206.49	8.415%	$223.8661	$223.87	$223.85	$223.90
Purchase #6	$170.84	7.650%	$183.9093	$183.91	$183.90	$183.90
Purchase #7	$14.32	8.626%	$15.5552	$15.56	$15.55	$15.60
7 purchase totals =	$893.34		$958.1618	$958.17	$958.15	$958.20