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	$133.31	8.444%	$144.5667	$144.57	$144.55	$144.60
Purchase #2	$227.52	9.753%	$249.71	$249.71	$249.70	$249.70
Purchase #3	$228.59	8.362%	$247.7047	$247.70	$247.70	$247.70
Purchase #4	$102.47	3.271%	$105.8218	$105.82	$105.80	$105.80
Purchase #5	$131.51	8.665%	$142.9053	$142.91	$142.90	$142.90
Purchase #6	$46.42	10.406%	$51.2505	$51.25	$51.25	$51.30
Purchase #7	$207.66	6.153%	$220.4373	$220.44	$220.45	$220.40
7 purchase totals =	$1,077.48		$1,162.3963	$1,162.40	$1,162.35	$1,162.40