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	$198.53	5.595%	$209.6378	$209.64	$209.65	$209.60
Purchase #2	$246.25	6.230%	$261.5914	$261.59	$261.60	$261.60
Purchase #3	$209.43	4.144%	$218.1088	$218.11	$218.10	$218.10
Purchase #4	$169.79	13.768%	$193.1667	$193.17	$193.15	$193.20
Purchase #5	$103.59	5.522%	$109.3102	$109.31	$109.30	$109.30
Purchase #6	$129.75	11.668%	$144.8892	$144.89	$144.90	$144.90
Purchase #7	$245.42	4.545%	$256.5743	$256.57	$256.55	$256.60
7 purchase totals =	$1,302.76		$1,393.2784	$1,393.28	$1,393.25	$1,393.30