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	$42.66	13.835%	$48.562	$48.56	$48.55	$48.60
Purchase #2	$162.35	13.806%	$184.764	$184.76	$184.75	$184.80
Purchase #3	$10.37	12.853%	$11.7029	$11.70	$11.70	$11.70
Purchase #4	$174.52	3.652%	$180.8935	$180.89	$180.90	$180.90
Purchase #5	$57.66	12.860%	$65.0751	$65.08	$65.10	$65.10
Purchase #6	$111.26	3.231%	$114.8548	$114.85	$114.85	$114.90
Purchase #7	$105.64	5.457%	$111.4048	$111.40	$111.40	$111.40
7 purchase totals =	$664.46		$717.2571	$717.24	$717.25	$717.40