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	$110.64	11.607%	$123.482	$123.48	$123.50	$123.50
Purchase #2	$167.46	10.146%	$184.4505	$184.45	$184.45	$184.50
Purchase #3	$194.60	4.774%	$203.8902	$203.89	$203.90	$203.90
Purchase #4	$150.53	8.116%	$162.747	$162.75	$162.75	$162.70
Purchase #5	$248.58	13.819%	$282.9313	$282.93	$282.95	$282.90
Purchase #6	$55.90	13.314%	$63.3425	$63.34	$63.35	$63.30
Purchase #7	$150.52	10.695%	$166.6181	$166.62	$166.60	$166.60
7 purchase totals =	$1,078.23		$1,187.4616	$1,187.46	$1,187.50	$1,187.40