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	$65.80	9.743%	$72.2109	$72.21	$72.20	$72.20
Purchase #2	$103.33	12.410%	$116.1533	$116.15	$116.15	$116.20
Purchase #3	$96.36	7.540%	$103.6255	$103.63	$103.65	$103.60
Purchase #4	$195.77	4.421%	$204.425	$204.43	$204.45	$204.40
Purchase #5	$66.78	6.537%	$71.1454	$71.15	$71.15	$71.10
Purchase #6	$209.86	4.724%	$219.7738	$219.77	$219.75	$219.80
Purchase #7	$167.66	4.191%	$174.6866	$174.69	$174.70	$174.70
7 purchase totals =	$905.56		$962.0205	$962.03	$962.05	$962.00