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	$234.38	11.539%	$261.4251	$261.43	$261.45	$261.40
Purchase #2	$83.27	8.620%	$90.4479	$90.45	$90.45	$90.40
Purchase #3	$137.89	13.807%	$156.9285	$156.93	$156.95	$156.90
Purchase #4	$209.92	8.102%	$226.9277	$226.93	$226.95	$226.90
Purchase #5	$135.79	3.827%	$140.9867	$140.99	$141.00	$141.00
Purchase #6	$123.36	10.180%	$135.918	$135.92	$135.90	$135.90
Purchase #7	$99.71	11.644%	$111.3202	$111.32	$111.30	$111.30
7 purchase totals =	$1,024.32		$1,123.9541	$1,123.97	$1,124.00	$1,123.80