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	$114.84	7.776%	$123.77	$123.77	$123.75	$123.80
Purchase #2	$132.34	7.107%	$141.7454	$141.75	$141.75	$141.70
Purchase #3	$177.63	7.310%	$190.6148	$190.61	$190.60	$190.60
Purchase #4	$115.27	3.114%	$118.8595	$118.86	$118.85	$118.90
Purchase #5	$233.43	13.104%	$264.0187	$264.02	$264.00	$264.00
Purchase #6	$21.71	7.424%	$23.3218	$23.32	$23.30	$23.30
Purchase #7	$38.43	9.662%	$42.1431	$42.14	$42.15	$42.10
7 purchase totals =	$833.65		$904.4733	$904.47	$904.40	$904.40