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	$60.56	7.206%	$64.924	$64.92	$64.90	$64.90
Purchase #2	$53.65	4.649%	$56.1442	$56.14	$56.15	$56.10
Purchase #3	$73.78	3.835%	$76.6095	$76.61	$76.60	$76.60
Purchase #4	$125.95	4.309%	$131.3772	$131.38	$131.40	$131.40
Purchase #5	$161.44	3.166%	$166.5512	$166.55	$166.55	$166.60
Purchase #6	$78.47	4.755%	$82.2012	$82.20	$82.20	$82.20
Purchase #7	$64.44	12.575%	$72.5433	$72.54	$72.55	$72.50
7 purchase totals =	$618.29		$650.3506	$650.34	$650.35	$650.30