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	$111.94	13.562%	$127.1213	$127.12	$127.10	$127.10
Purchase #2	$70.65	11.165%	$78.5381	$78.54	$78.55	$78.50
Purchase #3	$201.48	8.179%	$217.959	$217.96	$217.95	$218.00
Purchase #4	$91.93	6.314%	$97.7345	$97.73	$97.75	$97.70
Purchase #5	$16.64	11.413%	$18.5391	$18.54	$18.55	$18.50
Purchase #6	$207.48	3.809%	$215.3829	$215.38	$215.40	$215.40
Purchase #7	$29.53	8.705%	$32.1006	$32.10	$32.10	$32.10
7 purchase totals =	$729.65		$787.3755	$787.37	$787.40	$787.30