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	$227.54	5.222%	$239.4221	$239.42	$239.40	$239.40
Purchase #2	$160.96	3.771%	$167.0298	$167.03	$167.05	$167.00
Purchase #3	$52.54	13.122%	$59.4343	$59.43	$59.45	$59.40
Purchase #4	$98.56	10.234%	$108.6466	$108.65	$108.65	$108.60
Purchase #5	$197.45	10.832%	$218.8378	$218.84	$218.85	$218.80
Purchase #6	$221.88	5.297%	$233.633	$233.63	$233.65	$233.60
Purchase #7	$106.59	11.237%	$118.5675	$118.57	$118.55	$118.60
7 purchase totals =	$1,065.52		$1,145.5711	$1,145.57	$1,145.60	$1,145.40