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	$184.25	3.397%	$190.509	$190.51	$190.50	$190.50
Purchase #2	$79.58	12.444%	$89.4829	$89.48	$89.50	$89.50
Purchase #3	$8.59	3.140%	$8.8597	$8.86	$8.85	$8.90
Purchase #4	$123.37	13.559%	$140.0977	$140.10	$140.10	$140.10
Purchase #5	$49.33	6.724%	$52.6469	$52.65	$52.65	$52.60
Purchase #6	$110.76	9.606%	$121.3996	$121.40	$121.40	$121.40
Purchase #7	$115.49	10.510%	$127.628	$127.63	$127.65	$127.60
7 purchase totals =	$671.37		$730.6238	$730.63	$730.65	$730.60