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	$121.64	5.264%	$128.0431	$128.04	$128.05	$128.00
Purchase #2	$116.69	5.304%	$122.8792	$122.88	$122.90	$122.90
Purchase #3	$214.32	4.772%	$224.5474	$224.55	$224.55	$224.50
Purchase #4	$128.59	6.847%	$137.3946	$137.39	$137.40	$137.40
Purchase #5	$140.28	6.234%	$149.0251	$149.03	$149.05	$149.00
Purchase #6	$152.51	12.339%	$171.3282	$171.33	$171.35	$171.30
Purchase #7	$85.91	4.140%	$89.4667	$89.47	$89.45	$89.50
7 purchase totals =	$959.94		$1,022.6843	$1,022.69	$1,022.75	$1,022.60