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	$33.75	4.593%	$35.3001	$35.30	$35.30	$35.30
Purchase #2	$134.76	3.666%	$139.7003	$139.70	$139.70	$139.70
Purchase #3	$92.52	13.158%	$104.6938	$104.69	$104.70	$104.70
Purchase #4	$131.89	4.550%	$137.891	$137.89	$137.90	$137.90
Purchase #5	$170.30	10.404%	$188.018	$188.02	$188.00	$188.00
Purchase #6	$199.43	4.320%	$208.0454	$208.05	$208.05	$208.00
Purchase #7	$107.65	4.243%	$112.2176	$112.22	$112.20	$112.20
7 purchase totals =	$870.30		$925.8662	$925.87	$925.85	$925.80