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	$170.69	8.865%	$185.8217	$185.82	$185.80	$185.80
Purchase #2	$105.33	7.800%	$113.5457	$113.55	$113.55	$113.50
Purchase #3	$166.55	9.421%	$182.2407	$182.24	$182.25	$182.20
Purchase #4	$119.33	13.311%	$135.214	$135.21	$135.20	$135.20
Purchase #5	$82.31	9.294%	$89.9599	$89.96	$89.95	$90.00
Purchase #6	$191.76	4.584%	$200.5503	$200.55	$200.55	$200.60
Purchase #7	$109.61	7.710%	$118.0609	$118.06	$118.05	$118.10
7 purchase totals =	$945.58		$1,025.3932	$1,025.39	$1,025.35	$1,025.40