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	$129.48	12.352%	$145.4734	$145.47	$145.45	$145.50
Purchase #2	$41.44	5.370%	$43.6653	$43.67	$43.65	$43.70
Purchase #3	$248.26	13.436%	$281.6162	$281.62	$281.60	$281.60
Purchase #4	$99.59	9.464%	$109.0152	$109.02	$109.00	$109.00
Purchase #5	$116.32	3.770%	$120.7053	$120.71	$120.70	$120.70
Purchase #6	$80.81	10.672%	$89.434	$89.43	$89.45	$89.40
Purchase #7	$249.56	5.720%	$263.8348	$263.83	$263.85	$263.80
7 purchase totals =	$965.46		$1,053.7442	$1,053.75	$1,053.70	$1,053.70