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	$144.54	9.752%	$158.6355	$158.64	$158.65	$158.60
Purchase #2	$75.70	7.715%	$81.5403	$81.54	$81.55	$81.50
Purchase #3	$146.87	6.404%	$156.2756	$156.28	$156.30	$156.30
Purchase #4	$226.52	5.835%	$239.7374	$239.74	$239.75	$239.70
Purchase #5	$147.51	13.144%	$166.8987	$166.90	$166.90	$166.90
Purchase #6	$157.84	13.476%	$179.1105	$179.11	$179.10	$179.10
Purchase #7	$19.81	4.809%	$20.7627	$20.76	$20.75	$20.80
7 purchase totals =	$918.79		$1,002.9607	$1,002.97	$1,003.00	$1,002.90