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	$158.51	3.503%	$164.0626	$164.06	$164.05	$164.10
Purchase #2	$114.41	5.372%	$120.5561	$120.56	$120.55	$120.60
Purchase #3	$167.59	13.700%	$190.5498	$190.55	$190.55	$190.50
Purchase #4	$89.65	11.576%	$100.0279	$100.03	$100.05	$100.00
Purchase #5	$90.31	6.659%	$96.3237	$96.32	$96.30	$96.30
Purchase #6	$152.99	9.512%	$167.5424	$167.54	$167.55	$167.50
Purchase #7	$171.74	7.694%	$184.9537	$184.95	$184.95	$185.00
7 purchase totals =	$945.20		$1,024.0162	$1,024.01	$1,024.00	$1,024.00