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	$244.47	11.201%	$271.8531	$271.85	$271.85	$271.90
Purchase #2	$43.53	11.500%	$48.536	$48.54	$48.55	$48.50
Purchase #3	$182.87	7.486%	$196.5596	$196.56	$196.55	$196.60
Purchase #4	$160.94	3.343%	$166.3202	$166.32	$166.30	$166.30
Purchase #5	$246.86	10.330%	$272.3606	$272.36	$272.35	$272.40
Purchase #6	$64.85	12.862%	$73.191	$73.19	$73.20	$73.20
Purchase #7	$238.75	4.866%	$250.3676	$250.37	$250.35	$250.40
7 purchase totals =	$1,182.27		$1,279.1881	$1,279.19	$1,279.15	$1,279.30