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	$157.52	4.500%	$164.6084	$164.61	$164.60	$164.60
Purchase #2	$234.90	10.603%	$259.8064	$259.81	$259.80	$259.80
Purchase #3	$45.33	3.465%	$46.9007	$46.90	$46.90	$46.90
Purchase #4	$220.88	5.463%	$232.9467	$232.95	$232.95	$232.90
Purchase #5	$220.54	6.162%	$234.1297	$234.13	$234.15	$234.10
Purchase #6	$58.45	5.662%	$61.7594	$61.76	$61.75	$61.80
Purchase #7	$94.81	9.332%	$103.6577	$103.66	$103.65	$103.70
7 purchase totals =	$1,032.43		$1,103.8090	$1,103.82	$1,103.80	$1,103.80