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	$49.57	8.667%	$53.8662	$53.87	$53.85	$53.90
Purchase #2	$49.48	4.464%	$51.6888	$51.69	$51.70	$51.70
Purchase #3	$137.46	3.444%	$142.1941	$142.19	$142.20	$142.20
Purchase #4	$192.76	11.720%	$215.3515	$215.35	$215.35	$215.40
Purchase #5	$128.91	12.321%	$144.793	$144.79	$144.80	$144.80
Purchase #6	$196.90	12.460%	$221.4337	$221.43	$221.45	$221.40
Purchase #7	$107.31	3.405%	$110.9639	$110.96	$110.95	$111.00
7 purchase totals =	$862.39		$940.2912	$940.28	$940.30	$940.40