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	$167.82	12.185%	$188.2689	$188.27	$188.25	$188.30
Purchase #2	$101.76	4.533%	$106.3728	$106.37	$106.35	$106.40
Purchase #3	$82.75	7.417%	$88.8876	$88.89	$88.90	$88.90
Purchase #4	$79.56	5.130%	$83.6414	$83.64	$83.65	$83.60
Purchase #5	$79.42	3.127%	$81.9035	$81.90	$81.90	$81.90
Purchase #6	$170.27	7.410%	$182.887	$182.89	$182.90	$182.90
Purchase #7	$205.60	12.338%	$230.9669	$230.97	$230.95	$231.00
7 purchase totals =	$887.18		$962.9281	$962.93	$962.90	$963.00