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	$146.97	7.873%	$158.5409	$158.54	$158.55	$158.50
Purchase #2	$90.46	6.759%	$96.5742	$96.57	$96.55	$96.60
Purchase #3	$47.31	12.832%	$53.3808	$53.38	$53.40	$53.40
Purchase #4	$31.29	6.385%	$33.2879	$33.29	$33.30	$33.30
Purchase #5	$179.98	5.798%	$190.4152	$190.42	$190.40	$190.40
Purchase #6	$241.83	13.117%	$273.5508	$273.55	$273.55	$273.60
Purchase #7	$215.42	4.187%	$224.4396	$224.44	$224.45	$224.40
7 purchase totals =	$953.26		$1,030.1894	$1,030.19	$1,030.20	$1,030.20