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	$179.27	13.433%	$203.3513	$203.35	$203.35	$203.40
Purchase #2	$215.86	9.430%	$236.2156	$236.22	$236.20	$236.20
Purchase #3	$39.68	12.193%	$44.5182	$44.52	$44.50	$44.50
Purchase #4	$174.48	6.275%	$185.4286	$185.43	$185.45	$185.40
Purchase #5	$94.41	5.771%	$99.8584	$99.86	$99.85	$99.90
Purchase #6	$71.99	7.309%	$77.2517	$77.25	$77.25	$77.30
Purchase #7	$159.55	8.138%	$172.5342	$172.53	$172.55	$172.50
7 purchase totals =	$935.24		$1,019.1580	$1,019.16	$1,019.15	$1,019.20