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	$85.81	12.853%	$96.8392	$96.84	$96.85	$96.80
Purchase #2	$147.50	3.237%	$152.2746	$152.27	$152.25	$152.30
Purchase #3	$245.88	11.420%	$273.9595	$273.96	$273.95	$274.00
Purchase #4	$51.59	5.543%	$54.4496	$54.45	$54.45	$54.40
Purchase #5	$212.82	8.659%	$231.2481	$231.25	$231.25	$231.20
Purchase #6	$185.32	9.173%	$202.3194	$202.32	$202.30	$202.30
Purchase #7	$56.70	10.408%	$62.6013	$62.60	$62.60	$62.60
7 purchase totals =	$985.62		$1,073.6917	$1,073.69	$1,073.65	$1,073.60