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	$138.60	4.658%	$145.056	$145.06	$145.05	$145.10
Purchase #2	$59.30	10.596%	$65.5834	$65.58	$65.60	$65.60
Purchase #3	$189.68	5.853%	$200.782	$200.78	$200.80	$200.80
Purchase #4	$147.70	13.747%	$168.0043	$168.00	$168.00	$168.00
Purchase #5	$104.58	11.259%	$116.3547	$116.35	$116.35	$116.40
Purchase #6	$214.27	13.510%	$243.2179	$243.22	$243.20	$243.20
Purchase #7	$120.75	4.677%	$126.3975	$126.40	$126.40	$126.40
7 purchase totals =	$974.88		$1,065.3958	$1,065.39	$1,065.40	$1,065.50