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	$111.35	8.507%	$120.8225	$120.82	$120.80	$120.80
Purchase #2	$201.40	7.837%	$217.1837	$217.18	$217.20	$217.20
Purchase #3	$167.85	6.196%	$178.25	$178.25	$178.25	$178.30
Purchase #4	$125.72	5.629%	$132.7968	$132.80	$132.80	$132.80
Purchase #5	$86.55	5.696%	$91.4799	$91.48	$91.50	$91.50
Purchase #6	$200.90	9.438%	$219.8609	$219.86	$219.85	$219.90
Purchase #7	$81.26	11.447%	$90.5618	$90.56	$90.55	$90.60
7 purchase totals =	$975.03		$1,050.9556	$1,050.95	$1,050.95	$1,051.10