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	$92.32	9.109%	$100.7294	$100.73	$100.75	$100.70
Purchase #2	$13.55	13.508%	$15.3803	$15.38	$15.40	$15.40
Purchase #3	$184.53	10.221%	$203.3908	$203.39	$203.40	$203.40
Purchase #4	$131.95	9.279%	$144.1936	$144.19	$144.20	$144.20
Purchase #5	$232.39	5.488%	$245.1436	$245.14	$245.15	$245.10
Purchase #6	$217.72	13.511%	$247.1361	$247.14	$247.15	$247.10
Purchase #7	$43.97	3.274%	$45.4096	$45.41	$45.40	$45.40
7 purchase totals =	$916.43		$1,001.3834	$1,001.38	$1,001.45	$1,001.30