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	$185.56	10.566%	$205.1663	$205.17	$205.15	$205.20
Purchase #2	$176.48	9.867%	$193.8933	$193.89	$193.90	$193.90
Purchase #3	$104.83	13.173%	$118.6393	$118.64	$118.65	$118.60
Purchase #4	$47.65	13.241%	$53.9593	$53.96	$53.95	$54.00
Purchase #5	$152.49	13.318%	$172.7986	$172.80	$172.80	$172.80
Purchase #6	$131.91	3.582%	$136.635	$136.64	$136.65	$136.60
Purchase #7	$208.90	9.309%	$228.3465	$228.35	$228.35	$228.30
7 purchase totals =	$1,007.82		$1,109.4383	$1,109.45	$1,109.45	$1,109.40