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	$176.38	6.275%	$187.4478	$187.45	$187.45	$187.40
Purchase #2	$168.71	4.565%	$176.4116	$176.41	$176.40	$176.40
Purchase #3	$147.80	3.267%	$152.6286	$152.63	$152.65	$152.60
Purchase #4	$80.81	10.824%	$89.5569	$89.56	$89.55	$89.60
Purchase #5	$144.49	7.525%	$155.3629	$155.36	$155.35	$155.40
Purchase #6	$213.87	4.136%	$222.7157	$222.72	$222.70	$222.70
Purchase #7	$123.31	10.799%	$136.6262	$136.63	$136.65	$136.60
7 purchase totals =	$1,055.37		$1,120.7497	$1,120.76	$1,120.75	$1,120.70