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	$66.61	8.606%	$72.3425	$72.34	$72.35	$72.30
Purchase #2	$91.63	9.557%	$100.3871	$100.39	$100.40	$100.40
Purchase #3	$200.38	9.502%	$219.4201	$219.42	$219.40	$219.40
Purchase #4	$86.34	4.796%	$90.4809	$90.48	$90.50	$90.50
Purchase #5	$126.25	7.269%	$135.4271	$135.43	$135.45	$135.40
Purchase #6	$167.29	12.831%	$188.755	$188.76	$188.75	$188.80
Purchase #7	$117.73	5.414%	$124.1039	$124.10	$124.10	$124.10
7 purchase totals =	$856.23		$930.9166	$930.92	$930.95	$930.90