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	$80.53	13.728%	$91.5852	$91.59	$91.60	$91.60
Purchase #2	$29.98	7.199%	$32.1383	$32.14	$32.15	$32.10
Purchase #3	$57.96	7.120%	$62.0868	$62.09	$62.10	$62.10
Purchase #4	$114.58	7.798%	$123.5149	$123.51	$123.50	$123.50
Purchase #5	$117.56	6.175%	$124.8193	$124.82	$124.80	$124.80
Purchase #6	$190.97	7.369%	$205.0426	$205.04	$205.05	$205.00
Purchase #7	$156.86	5.728%	$165.8449	$165.84	$165.85	$165.80
7 purchase totals =	$748.44		$805.0320	$805.03	$805.05	$804.90