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	$113.44	4.308%	$118.327	$118.33	$118.35	$118.30
Purchase #2	$85.77	12.415%	$96.4183	$96.42	$96.40	$96.40
Purchase #3	$76.78	7.490%	$82.5308	$82.53	$82.55	$82.50
Purchase #4	$83.94	10.427%	$92.6924	$92.69	$92.70	$92.70
Purchase #5	$166.56	4.859%	$174.6532	$174.65	$174.65	$174.70
Purchase #6	$103.62	9.381%	$113.3406	$113.34	$113.35	$113.30
Purchase #7	$73.87	6.208%	$78.4558	$78.46	$78.45	$78.50
7 purchase totals =	$703.98		$756.4181	$756.42	$756.45	$756.40