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	$98.30	11.864%	$109.9623	$109.96	$109.95	$110.00
Purchase #2	$150.48	10.141%	$165.7402	$165.74	$165.75	$165.70
Purchase #3	$173.97	3.596%	$180.226	$180.23	$180.25	$180.20
Purchase #4	$17.37	5.565%	$18.3366	$18.34	$18.35	$18.30
Purchase #5	$34.64	9.545%	$37.9464	$37.95	$37.95	$37.90
Purchase #6	$166.49	3.398%	$172.1473	$172.15	$172.15	$172.10
Purchase #7	$35.33	10.551%	$39.0577	$39.06	$39.05	$39.10
7 purchase totals =	$676.58		$723.4165	$723.43	$723.45	$723.30