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	$112.83	12.796%	$127.2677	$127.27	$127.25	$127.30
Purchase #2	$196.39	3.730%	$203.7153	$203.72	$203.70	$203.70
Purchase #3	$161.43	12.729%	$181.9784	$181.98	$182.00	$182.00
Purchase #4	$8.37	9.219%	$9.1416	$9.14	$9.15	$9.10
Purchase #5	$48.48	12.236%	$54.412	$54.41	$54.40	$54.40
Purchase #6	$46.33	7.443%	$49.7783	$49.78	$49.80	$49.80
Purchase #7	$93.33	7.222%	$100.0703	$100.07	$100.05	$100.10
7 purchase totals =	$667.16		$726.3636	$726.37	$726.35	$726.40