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	$69.51	7.168%	$74.4925	$74.49	$74.50	$74.50
Purchase #2	$54.26	4.258%	$56.5704	$56.57	$56.55	$56.60
Purchase #3	$149.57	10.585%	$165.402	$165.40	$165.40	$165.40
Purchase #4	$117.80	4.745%	$123.3896	$123.39	$123.40	$123.40
Purchase #5	$7.30	7.484%	$7.8463	$7.85	$7.85	$7.80
Purchase #6	$201.44	6.747%	$215.0312	$215.03	$215.05	$215.00
Purchase #7	$99.40	4.443%	$103.8163	$103.82	$103.80	$103.80
7 purchase totals =	$699.28		$746.5483	$746.55	$746.55	$746.50