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	$226.52	7.864%	$244.3335	$244.33	$244.35	$244.30
Purchase #2	$137.53	8.285%	$148.9244	$148.92	$148.90	$148.90
Purchase #3	$46.37	13.781%	$52.7602	$52.76	$52.75	$52.80
Purchase #4	$58.64	7.646%	$63.1236	$63.12	$63.10	$63.10
Purchase #5	$239.48	3.359%	$247.5241	$247.52	$247.50	$247.50
Purchase #6	$54.64	10.654%	$60.4613	$60.46	$60.45	$60.50
Purchase #7	$77.92	6.241%	$82.783	$82.78	$82.80	$82.80
7 purchase totals =	$841.10		$899.9101	$899.89	$899.85	$899.90