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	$51.65	5.641%	$54.5636	$54.56	$54.55	$54.60
Purchase #2	$57.33	6.172%	$60.8684	$60.87	$60.85	$60.90
Purchase #3	$123.43	11.199%	$137.2529	$137.25	$137.25	$137.30
Purchase #4	$155.32	7.204%	$166.5093	$166.51	$166.50	$166.50
Purchase #5	$89.63	7.163%	$96.0502	$96.05	$96.05	$96.10
Purchase #6	$244.48	5.626%	$258.2344	$258.23	$258.25	$258.20
Purchase #7	$128.59	3.111%	$132.5904	$132.59	$132.60	$132.60
7 purchase totals =	$850.43		$906.0692	$906.06	$906.05	$906.20