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	$38.35	13.133%	$43.3865	$43.39	$43.40	$43.40
Purchase #2	$222.53	4.816%	$233.247	$233.25	$233.25	$233.20
Purchase #3	$157.30	6.353%	$167.2933	$167.29	$167.30	$167.30
Purchase #4	$134.50	4.277%	$140.2526	$140.25	$140.25	$140.30
Purchase #5	$113.46	8.793%	$123.4365	$123.44	$123.45	$123.40
Purchase #6	$203.62	8.573%	$221.0763	$221.08	$221.10	$221.10
Purchase #7	$143.63	6.302%	$152.6816	$152.68	$152.70	$152.70
7 purchase totals =	$1,013.39		$1,081.3738	$1,081.38	$1,081.45	$1,081.40