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	$111.74	13.685%	$127.0316	$127.03	$127.05	$127.00
Purchase #2	$212.52	5.726%	$224.6889	$224.69	$224.70	$224.70
Purchase #3	$217.33	3.122%	$224.115	$224.12	$224.10	$224.10
Purchase #4	$19.92	4.480%	$20.8124	$20.81	$20.80	$20.80
Purchase #5	$196.86	12.795%	$222.0482	$222.05	$222.05	$222.00
Purchase #6	$114.63	11.355%	$127.6462	$127.65	$127.65	$127.60
Purchase #7	$138.82	12.778%	$156.5584	$156.56	$156.55	$156.60
7 purchase totals =	$1,011.82		$1,102.9007	$1,102.91	$1,102.90	$1,102.80