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	$6.38	8.816%	$6.9425	$6.94	$6.95	$6.90
Purchase #2	$82.96	13.171%	$93.8867	$93.89	$93.90	$93.90
Purchase #3	$201.38	10.399%	$222.3215	$222.32	$222.30	$222.30
Purchase #4	$190.74	4.860%	$200.01	$200.01	$200.00	$200.00
Purchase #5	$113.90	8.610%	$123.7068	$123.71	$123.70	$123.70
Purchase #6	$94.62	3.728%	$98.1474	$98.15	$98.15	$98.10
Purchase #7	$43.91	12.579%	$49.4334	$49.43	$49.45	$49.40
7 purchase totals =	$733.89		$794.4483	$794.45	$794.45	$794.30