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	$86.99	13.123%	$98.4057	$98.41	$98.40	$98.40
Purchase #2	$225.49	13.651%	$256.2716	$256.27	$256.25	$256.30
Purchase #3	$156.75	3.445%	$162.15	$162.15	$162.15	$162.20
Purchase #4	$5.49	4.782%	$5.7525	$5.75	$5.75	$5.80
Purchase #5	$48.74	5.864%	$51.5981	$51.60	$51.60	$51.60
Purchase #6	$141.71	7.338%	$152.1087	$152.11	$152.10	$152.10
Purchase #7	$95.29	5.266%	$100.308	$100.31	$100.30	$100.30
7 purchase totals =	$760.46		$826.5946	$826.60	$826.55	$826.70