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	$227.49	4.863%	$238.5528	$238.55	$238.55	$238.60
Purchase #2	$205.63	6.512%	$219.0206	$219.02	$219.00	$219.00
Purchase #3	$70.57	7.129%	$75.6009	$75.60	$75.60	$75.60
Purchase #4	$59.86	13.301%	$67.822	$67.82	$67.80	$67.80
Purchase #5	$91.57	7.563%	$98.4954	$98.50	$98.50	$98.50
Purchase #6	$36.32	3.866%	$37.7241	$37.72	$37.70	$37.70
Purchase #7	$42.50	11.555%	$47.4109	$47.41	$47.40	$47.40
7 purchase totals =	$733.94		$784.6267	$784.62	$784.55	$784.60