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	$103.25	11.288%	$114.9049	$114.90	$114.90	$114.90
Purchase #2	$136.35	8.825%	$148.3829	$148.38	$148.40	$148.40
Purchase #3	$53.62	10.546%	$59.2748	$59.27	$59.25	$59.30
Purchase #4	$246.87	9.872%	$271.241	$271.24	$271.25	$271.20
Purchase #5	$67.85	5.569%	$71.6286	$71.63	$71.65	$71.60
Purchase #6	$170.66	7.368%	$183.2342	$183.23	$183.25	$183.20
Purchase #7	$158.94	7.149%	$170.3026	$170.30	$170.30	$170.30
7 purchase totals =	$937.54		$1,018.9690	$1,018.95	$1,019.00	$1,018.90