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	$128.63	10.714%	$142.4114	$142.41	$142.40	$142.40
Purchase #2	$100.48	12.528%	$113.0681	$113.07	$113.05	$113.10
Purchase #3	$83.53	7.530%	$89.8198	$89.82	$89.80	$89.80
Purchase #4	$150.76	12.304%	$169.3095	$169.31	$169.30	$169.30
Purchase #5	$46.96	12.835%	$52.9873	$52.99	$53.00	$53.00
Purchase #6	$87.58	6.447%	$93.2263	$93.23	$93.25	$93.20
Purchase #7	$30.75	9.501%	$33.6716	$33.67	$33.65	$33.70
7 purchase totals =	$628.69		$694.4940	$694.50	$694.45	$694.50