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	$186.47	4.784%	$195.3907	$195.39	$195.40	$195.40
Purchase #2	$40.88	3.850%	$42.4539	$42.45	$42.45	$42.50
Purchase #3	$238.82	12.136%	$267.8032	$267.80	$267.80	$267.80
Purchase #4	$48.55	9.683%	$53.2511	$53.25	$53.25	$53.30
Purchase #5	$47.41	9.832%	$52.0714	$52.07	$52.05	$52.10
Purchase #6	$242.55	12.285%	$272.3473	$272.35	$272.35	$272.30
Purchase #7	$110.77	12.448%	$124.5586	$124.56	$124.55	$124.60
7 purchase totals =	$915.45		$1,007.8762	$1,007.87	$1,007.85	$1,008.00