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	$167.78	9.294%	$183.3735	$183.37	$183.35	$183.40
Purchase #2	$71.47	11.360%	$79.589	$79.59	$79.60	$79.60
Purchase #3	$24.38	13.383%	$27.6428	$27.64	$27.65	$27.60
Purchase #4	$44.39	10.131%	$48.8872	$48.89	$48.90	$48.90
Purchase #5	$34.52	8.374%	$37.4107	$37.41	$37.40	$37.40
Purchase #6	$72.98	5.783%	$77.2004	$77.20	$77.20	$77.20
Purchase #7	$10.93	4.675%	$11.441	$11.44	$11.45	$11.40
7 purchase totals =	$426.45		$465.5446	$465.54	$465.55	$465.50