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	$115.94	11.185%	$128.9079	$128.91	$128.90	$128.90
Purchase #2	$13.81	3.627%	$14.3109	$14.31	$14.30	$14.30
Purchase #3	$199.47	12.763%	$224.9284	$224.93	$224.95	$224.90
Purchase #4	$58.38	5.462%	$61.5687	$61.57	$61.55	$61.60
Purchase #5	$178.77	7.162%	$191.5735	$191.57	$191.55	$191.60
Purchase #6	$160.39	4.360%	$167.383	$167.38	$167.40	$167.40
Purchase #7	$105.78	5.665%	$111.7724	$111.77	$111.75	$111.80
7 purchase totals =	$832.54		$900.4448	$900.44	$900.40	$900.50