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	$114.81	11.824%	$128.3851	$128.39	$128.40	$128.40
Purchase #2	$105.71	12.650%	$119.0823	$119.08	$119.10	$119.10
Purchase #3	$33.33	12.726%	$37.5716	$37.57	$37.55	$37.60
Purchase #4	$224.37	4.186%	$233.7621	$233.76	$233.75	$233.80
Purchase #5	$147.35	8.769%	$160.2711	$160.27	$160.25	$160.30
Purchase #6	$159.60	5.499%	$168.3764	$168.38	$168.40	$168.40
Purchase #7	$151.40	11.383%	$168.6339	$168.63	$168.65	$168.60
7 purchase totals =	$936.57		$1,016.0825	$1,016.08	$1,016.10	$1,016.20