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	$157.90	4.148%	$164.4497	$164.45	$164.45	$164.40
Purchase #2	$190.51	4.576%	$199.2277	$199.23	$199.25	$199.20
Purchase #3	$81.56	13.368%	$92.4629	$92.46	$92.45	$92.50
Purchase #4	$222.45	7.848%	$239.9079	$239.91	$239.90	$239.90
Purchase #5	$86.44	4.689%	$90.4932	$90.49	$90.50	$90.50
Purchase #6	$123.83	6.521%	$131.905	$131.91	$131.90	$131.90
Purchase #7	$41.97	5.425%	$44.2469	$44.25	$44.25	$44.20
7 purchase totals =	$904.66		$962.6933	$962.70	$962.70	$962.60