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	$142.39	3.424%	$147.2654	$147.27	$147.25	$147.30
Purchase #2	$49.38	7.726%	$53.1951	$53.20	$53.20	$53.20
Purchase #3	$132.75	10.193%	$146.2812	$146.28	$146.30	$146.30
Purchase #4	$54.66	12.181%	$61.3181	$61.32	$61.30	$61.30
Purchase #5	$220.66	4.737%	$231.1127	$231.11	$231.10	$231.10
Purchase #6	$164.85	11.298%	$183.4748	$183.47	$183.45	$183.50
Purchase #7	$53.29	5.626%	$56.2881	$56.29	$56.30	$56.30
7 purchase totals =	$817.98		$878.9354	$878.94	$878.90	$879.00