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	$86.54	5.251%	$91.0842	$91.08	$91.10	$91.10
Purchase #2	$14.43	6.256%	$15.3327	$15.33	$15.35	$15.30
Purchase #3	$19.87	8.171%	$21.4936	$21.49	$21.50	$21.50
Purchase #4	$32.71	12.656%	$36.8498	$36.85	$36.85	$36.80
Purchase #5	$37.86	12.335%	$42.53	$42.53	$42.55	$42.50
Purchase #6	$167.51	6.289%	$178.0447	$178.04	$178.05	$178.00
Purchase #7	$17.66	8.254%	$19.1177	$19.12	$19.10	$19.10
7 purchase totals =	$376.58		$404.4527	$404.44	$404.50	$404.30