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	$87.69	3.148%	$90.4505	$90.45	$90.45	$90.50
Purchase #2	$228.62	4.683%	$239.3263	$239.33	$239.35	$239.30
Purchase #3	$191.43	4.752%	$200.5268	$200.53	$200.55	$200.50
Purchase #4	$161.48	11.308%	$179.7402	$179.74	$179.75	$179.70
Purchase #5	$142.45	9.139%	$155.4685	$155.47	$155.45	$155.50
Purchase #6	$218.52	3.634%	$226.461	$226.46	$226.45	$226.50
Purchase #7	$139.57	3.450%	$144.3852	$144.39	$144.40	$144.40
7 purchase totals =	$1,169.76		$1,236.3585	$1,236.37	$1,236.40	$1,236.40