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	$49.99	7.310%	$53.6443	$53.64	$53.65	$53.60
Purchase #2	$171.39	11.718%	$191.4735	$191.47	$191.45	$191.50
Purchase #3	$100.87	11.653%	$112.6244	$112.62	$112.60	$112.60
Purchase #4	$56.42	3.222%	$58.2379	$58.24	$58.25	$58.20
Purchase #5	$169.86	10.276%	$187.3148	$187.31	$187.30	$187.30
Purchase #6	$47.48	8.481%	$51.5068	$51.51	$51.50	$51.50
Purchase #7	$212.81	7.846%	$229.5071	$229.51	$229.50	$229.50
7 purchase totals =	$808.82		$884.3088	$884.30	$884.25	$884.20