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	$141.31	8.691%	$153.5913	$153.59	$153.60	$153.60
Purchase #2	$94.75	13.570%	$107.6076	$107.61	$107.60	$107.60
Purchase #3	$131.38	11.818%	$146.9065	$146.91	$146.90	$146.90
Purchase #4	$29.94	10.404%	$33.055	$33.06	$33.05	$33.10
Purchase #5	$36.91	7.370%	$39.6303	$39.63	$39.65	$39.60
Purchase #6	$224.67	9.428%	$245.8519	$245.85	$245.85	$245.90
Purchase #7	$137.74	10.841%	$152.6724	$152.67	$152.65	$152.70
7 purchase totals =	$796.70		$879.3150	$879.32	$879.30	$879.40