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	$116.27	13.767%	$132.2769	$132.28	$132.30	$132.30
Purchase #2	$48.31	5.657%	$51.0429	$51.04	$51.05	$51.00
Purchase #3	$51.62	5.677%	$54.5505	$54.55	$54.55	$54.60
Purchase #4	$83.52	6.649%	$89.0732	$89.07	$89.05	$89.10
Purchase #5	$41.76	13.727%	$47.4924	$47.49	$47.50	$47.50
Purchase #6	$221.89	8.675%	$241.139	$241.14	$241.15	$241.10
Purchase #7	$79.96	6.522%	$85.175	$85.18	$85.20	$85.20
7 purchase totals =	$643.33		$700.7499	$700.75	$700.80	$700.80