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	$106.57	3.553%	$110.3564	$110.36	$110.35	$110.40
Purchase #2	$32.72	12.820%	$36.9147	$36.91	$36.90	$36.90
Purchase #3	$17.41	10.476%	$19.2339	$19.23	$19.25	$19.20
Purchase #4	$226.53	12.763%	$255.442	$255.44	$255.45	$255.40
Purchase #5	$101.54	7.803%	$109.4632	$109.46	$109.45	$109.50
Purchase #6	$125.70	12.291%	$141.1498	$141.15	$141.15	$141.10
Purchase #7	$131.46	7.626%	$141.4851	$141.49	$141.50	$141.50
7 purchase totals =	$741.93		$814.0451	$814.04	$814.05	$814.00