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	$57.95	11.356%	$64.5308	$64.53	$64.55	$64.50
Purchase #2	$136.93	10.727%	$151.6185	$151.62	$151.60	$151.60
Purchase #3	$101.78	6.723%	$108.6227	$108.62	$108.60	$108.60
Purchase #4	$168.92	12.809%	$190.557	$190.56	$190.55	$190.60
Purchase #5	$92.71	4.151%	$96.5584	$96.56	$96.55	$96.60
Purchase #6	$245.89	4.328%	$256.5321	$256.53	$256.55	$256.50
Purchase #7	$249.89	4.607%	$261.4024	$261.40	$261.40	$261.40
7 purchase totals =	$1,054.07		$1,129.8219	$1,129.82	$1,129.80	$1,129.80