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	$114.92	7.836%	$123.9251	$123.93	$123.95	$123.90
Purchase #2	$32.42	8.703%	$35.2415	$35.24	$35.25	$35.20
Purchase #3	$156.31	5.142%	$164.3475	$164.35	$164.35	$164.30
Purchase #4	$12.43	3.534%	$12.8693	$12.87	$12.85	$12.90
Purchase #5	$84.29	7.435%	$90.557	$90.56	$90.55	$90.60
Purchase #6	$41.33	12.791%	$46.6165	$46.62	$46.60	$46.60
Purchase #7	$23.35	6.558%	$24.8813	$24.88	$24.90	$24.90
7 purchase totals =	$465.05		$498.4382	$498.45	$498.45	$498.40