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	$55.80	12.666%	$62.8676	$62.87	$62.85	$62.90
Purchase #2	$98.27	10.234%	$108.327	$108.33	$108.35	$108.30
Purchase #3	$122.60	12.117%	$137.4554	$137.46	$137.45	$137.50
Purchase #4	$102.80	9.108%	$112.163	$112.16	$112.15	$112.20
Purchase #5	$97.92	6.566%	$104.3494	$104.35	$104.35	$104.30
Purchase #6	$136.31	11.220%	$151.604	$151.60	$151.60	$151.60
Purchase #7	$78.60	6.403%	$83.6328	$83.63	$83.65	$83.60
7 purchase totals =	$692.30		$760.3992	$760.40	$760.40	$760.40