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	$176.94	11.192%	$196.7431	$196.74	$196.75	$196.70
Purchase #2	$249.93	3.398%	$258.4226	$258.42	$258.40	$258.40
Purchase #3	$238.77	8.165%	$258.2656	$258.27	$258.25	$258.30
Purchase #4	$248.82	4.395%	$259.7556	$259.76	$259.75	$259.80
Purchase #5	$233.47	13.120%	$264.1013	$264.10	$264.10	$264.10
Purchase #6	$131.52	11.545%	$146.704	$146.70	$146.70	$146.70
Purchase #7	$113.56	12.475%	$127.7266	$127.73	$127.75	$127.70
7 purchase totals =	$1,393.01		$1,511.7188	$1,511.72	$1,511.70	$1,511.70