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	$92.97	13.336%	$105.3685	$105.37	$105.35	$105.40
Purchase #2	$82.86	7.724%	$89.2601	$89.26	$89.25	$89.30
Purchase #3	$22.60	11.130%	$25.1154	$25.12	$25.10	$25.10
Purchase #4	$67.96	6.243%	$72.2027	$72.20	$72.20	$72.20
Purchase #5	$47.47	9.167%	$51.8216	$51.82	$51.80	$51.80
Purchase #6	$93.84	4.656%	$98.2092	$98.21	$98.20	$98.20
Purchase #7	$140.51	5.181%	$147.7898	$147.79	$147.80	$147.80
7 purchase totals =	$548.21		$589.7673	$589.77	$589.70	$589.80