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	$33.61	4.790%	$35.2199	$35.22	$35.20	$35.20
Purchase #2	$42.34	7.533%	$45.5295	$45.53	$45.55	$45.50
Purchase #3	$95.43	8.804%	$103.8317	$103.83	$103.85	$103.80
Purchase #4	$181.51	4.258%	$189.2387	$189.24	$189.25	$189.20
Purchase #5	$240.38	10.378%	$265.3266	$265.33	$265.35	$265.30
Purchase #6	$122.71	11.664%	$137.0229	$137.02	$137.00	$137.00
Purchase #7	$19.27	9.250%	$21.0525	$21.05	$21.05	$21.10
7 purchase totals =	$735.25		$797.2218	$797.22	$797.25	$797.10