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	$161.61	6.673%	$172.3942	$172.39	$172.40	$172.40
Purchase #2	$157.26	4.488%	$164.3178	$164.32	$164.30	$164.30
Purchase #3	$160.77	4.760%	$168.4227	$168.42	$168.40	$168.40
Purchase #4	$131.67	13.585%	$149.5574	$149.56	$149.55	$149.60
Purchase #5	$85.60	5.834%	$90.5939	$90.59	$90.60	$90.60
Purchase #6	$167.63	9.736%	$183.9505	$183.95	$183.95	$184.00
Purchase #7	$105.46	12.263%	$118.3926	$118.39	$118.40	$118.40
7 purchase totals =	$970.00		$1,047.6291	$1,047.62	$1,047.60	$1,047.70