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	$92.71	13.264%	$105.0071	$105.01	$105.00	$105.00
Purchase #2	$42.30	13.753%	$48.1175	$48.12	$48.10	$48.10
Purchase #3	$24.50	3.472%	$25.3506	$25.35	$25.35	$25.40
Purchase #4	$167.50	12.133%	$187.8228	$187.82	$187.80	$187.80
Purchase #5	$64.37	10.243%	$70.9634	$70.96	$70.95	$71.00
Purchase #6	$162.60	3.797%	$168.7739	$168.77	$168.75	$168.80
Purchase #7	$77.52	3.648%	$80.3479	$80.35	$80.35	$80.30
7 purchase totals =	$631.50		$686.3832	$686.38	$686.30	$686.40