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	$93.82	10.260%	$103.4459	$103.45	$103.45	$103.40
Purchase #2	$34.97	10.745%	$38.7275	$38.73	$38.75	$38.70
Purchase #3	$152.45	8.172%	$164.9082	$164.91	$164.90	$164.90
Purchase #4	$196.37	8.221%	$212.5136	$212.51	$212.50	$212.50
Purchase #5	$222.63	11.637%	$248.5375	$248.54	$248.55	$248.50
Purchase #6	$198.56	5.374%	$209.2306	$209.23	$209.25	$209.20
Purchase #7	$176.57	7.864%	$190.4555	$190.46	$190.45	$190.50
7 purchase totals =	$1,075.37		$1,167.8188	$1,167.83	$1,167.85	$1,167.70