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	$53.48	4.799%	$56.0465	$56.05	$56.05	$56.00
Purchase #2	$109.33	13.662%	$124.2667	$124.27	$124.25	$124.30
Purchase #3	$76.61	5.366%	$80.7209	$80.72	$80.70	$80.70
Purchase #4	$122.47	6.662%	$130.629	$130.63	$130.65	$130.60
Purchase #5	$52.82	13.230%	$59.8081	$59.81	$59.80	$59.80
Purchase #6	$107.55	10.661%	$119.0159	$119.02	$119.00	$119.00
Purchase #7	$151.85	4.142%	$158.1396	$158.14	$158.15	$158.10
7 purchase totals =	$674.11		$728.6267	$728.64	$728.60	$728.50