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	$62.35	4.362%	$65.0697	$65.07	$65.05	$65.10
Purchase #2	$172.39	9.420%	$188.6291	$188.63	$188.65	$188.60
Purchase #3	$85.31	4.403%	$89.0662	$89.07	$89.05	$89.10
Purchase #4	$18.47	5.434%	$19.4737	$19.47	$19.45	$19.50
Purchase #5	$180.97	4.448%	$189.0195	$189.02	$189.00	$189.00
Purchase #6	$98.80	10.648%	$109.3202	$109.32	$109.30	$109.30
Purchase #7	$14.55	7.487%	$15.6394	$15.64	$15.65	$15.60
7 purchase totals =	$632.84		$676.2178	$676.22	$676.15	$676.20