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	$162.26	13.792%	$184.6389	$184.64	$184.65	$184.60
Purchase #2	$100.57	3.196%	$103.7842	$103.78	$103.80	$103.80
Purchase #3	$143.76	12.413%	$161.6049	$161.60	$161.60	$161.60
Purchase #4	$117.43	4.842%	$123.116	$123.12	$123.10	$123.10
Purchase #5	$45.70	3.132%	$47.1313	$47.13	$47.15	$47.10
Purchase #6	$127.42	12.736%	$143.6482	$143.65	$143.65	$143.60
Purchase #7	$86.42	9.752%	$94.8477	$94.85	$94.85	$94.80
7 purchase totals =	$783.56		$858.7712	$858.77	$858.80	$858.60