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	$128.97	10.726%	$142.8033	$142.80	$142.80	$142.80
Purchase #2	$50.42	3.110%	$51.9881	$51.99	$52.00	$52.00
Purchase #3	$188.77	4.196%	$196.6908	$196.69	$196.70	$196.70
Purchase #4	$159.25	8.209%	$172.3228	$172.32	$172.30	$172.30
Purchase #5	$65.65	9.504%	$71.8894	$71.89	$71.90	$71.90
Purchase #6	$124.80	5.692%	$131.9036	$131.90	$131.90	$131.90
Purchase #7	$145.40	13.685%	$165.298	$165.30	$165.30	$165.30
7 purchase totals =	$863.26		$932.8960	$932.89	$932.90	$932.90