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	$127.27	9.459%	$139.3085	$139.31	$139.30	$139.30
Purchase #2	$179.83	9.195%	$196.3654	$196.37	$196.35	$196.40
Purchase #3	$224.74	13.840%	$255.844	$255.84	$255.85	$255.80
Purchase #4	$100.47	8.773%	$109.2842	$109.28	$109.30	$109.30
Purchase #5	$189.65	7.303%	$203.5001	$203.50	$203.50	$203.50
Purchase #6	$190.68	12.507%	$214.5283	$214.53	$214.55	$214.50
Purchase #7	$54.84	13.468%	$62.2259	$62.23	$62.25	$62.20
7 purchase totals =	$1,067.48		$1,181.0564	$1,181.06	$1,181.10	$1,181.00