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	$154.49	13.871%	$175.9193	$175.92	$175.90	$175.90
Purchase #2	$174.83	4.378%	$182.4841	$182.48	$182.50	$182.50
Purchase #3	$171.42	4.565%	$179.2453	$179.25	$179.25	$179.20
Purchase #4	$199.31	9.873%	$218.9879	$218.99	$219.00	$219.00
Purchase #5	$166.44	3.720%	$172.6316	$172.63	$172.65	$172.60
Purchase #6	$50.36	10.585%	$55.6906	$55.69	$55.70	$55.70
Purchase #7	$141.35	3.636%	$146.4895	$146.49	$146.50	$146.50
7 purchase totals =	$1,058.20		$1,131.4483	$1,131.45	$1,131.50	$1,131.40